Books in academic libraries are usually arranged by the Library of Congress Classification System. This system keeps books on the same topic together on the shelves. Find the LC call number for a book using the USA catalog.
Each class is identified by one letter. (e.g. Q indicates science)
Sub classes are more finely identified by adding more letters. (e.g. QC indicates physics)
Sub classes are further broken down using whole numbers. ((e.g. QC 350 is optics)

You can use this system to go to the shelves and browse the area you are interested in.

Library of Congress Classification System

     
         A  General Works
              AE        Encyclopedias
              AG        General Reference Works
              AY        Yearbooks. Almanacs. Directories, etc.

         B  Philosophy. Psychology. Religion
              B         Philosopy (General)
              BF        Psychology
              BL        Religions
    
         C  Auxiliary Sciences of History (General)

         D  History (includes Travel)
              D         History(General)
                901-    Europe
              DA        Great Britain
              DB-DD     Central/Western Europe
              DE-DG     Mediterranean Region. Greece. Italy
              DP        Spain. Portugal
              DR        Eastern Europe
              DS        Asia
                701-    China
                801-    Japan
              DT        Africa
              DU        Oceania
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         E  America  

         F  Canada. United States. Latin America
                
         G  Geography
              G.        Geography (General)
              G 1000-   Atlases
              GA        Cartography
              GB        Physical geography
              GC        Oceanography
              GE        Environmental Sciences
              GF        Human ecology
              GV        Recreation. Leisure
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         H  Social Sciences
              H         Social Sciences (General)
              HA        Statistics
              HB-HC     Economics
              HD        Industry. Labor
              HE        Transportation. Communications
              HF        Commerce. Marketing. Advertising
                5383-   Resumes
                5410-   Marketing
                5500.2- Personnel
                5548.4- Business Data Processing
                        Electronic Speadsheets
                5549-   Personnel Management
                5601-   Accounting
                5717-   Business Communication
                5801-   Advertising
              HG        Finance
                201-    Money
                1501-   Banking
                4501-   Investment
              HJ        Public Finance
              HM-HX     Sociology
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         J  Political Science
              JF        General Works
              JF-JQ     Constitutional History
              JX        International Law

         K  Law
              K         Law (General)
              KE        Law of Canada (Federal)
              KEB       Law of British Columbia
              KEO       Law of Ontario

         L  Education
              L         Education (General)
              LB        Theory and Practice
              LC        Special Aspects

        M  Music
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        N  Fine Arts
              N         Visual Arts (General)
              NA        Architecture
              NC        Drawing. Design. Illustration
              NK        Decorative Arts. Interior Decorating

         P  Language and Literature
              P 101     Language (General)
              PE        English (including Dictionaries)
                1617-   Dictionaries (Modern)
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         Q  Science
              Q         Science (General)
              QA        Mathematics
                76.5-   Information Theory. Computer Science.
                        Electronic Data Processing.
                        Computer Programming
                76.76-  DOS/MS-DOS. Windows
                76.9.D3-Data Base Management
              QB        Astronomy
              QC        Physics
                350-    Optics
                501-    Electricity. Magnetism
                851-    Meteorology. Climatology
              QD        Chemistry
              QE        Geology
              QH        Natural History. Biology (General)
                540-    Ecology
              QK        Botany
              QL        Zoology
              QM        Human Anatomy
              QP        Physiology
              QR        Microbiology
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         R  Medicine
              R         Medicine (General)
               121-     Medical dictionaries
               724-     Ethics in Medicine
               856-     Biomedical Engineering
               895-     Medical Physics. Nuclear Medicine
              RA        Public Health
               776-     Personal Health & Wellness
               963-     Hospitals
               1190-    Toxicology
              RB        Pathology
               36-      Laboratories
               155-     Medical Genetics
              RC        Internal Medicine
               78-      Diagnosis (Ultrasound, Radiography, MRI)
               111-     Infectious Diseases
               261-     Cancer
               331-     Neurology. Psychiatry
               440-     Psychiatric Nursing
               565-     Alcohol & Drug Abuse
               607-     AIDS
               620.5-   Nutritional Diseases
               667-     The Heart / Cardiology
               801-     Musculoskeletal Diseases
               952-     Gerontology/Aging
               963-     Industrial (Occupational) Hygiene
             RD         Surgery
             RE-RF      Eyes, Ears, Nose & Throat
             RG         Gynecology. Obstetrics
             RJ         Pediatrics
             RM         Therapies (Radiation, Physical, Drug, etc.)
             RS 55-     Pharmaceutical Drugs
             RT         Nursing
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        S   Agriculture
             S          Agriculture (General)
             SB         Plant Culture. Horticulture
             SD         Forestry
             SF         Animal Culture
             SH         Aquaculture. Fisheries
             SK         Hunting. Wildlife Management

        T   Technology
             T          Technology (General)
              11-       Technical/Report Writing
              351-      Engineering Graphics
                        Mechanical Drawing
              385-      Computer Graphics
             TA         General Engineering
              166-      Human/Systems Engineering
              349-      Mechanics
              401-      Materials
              501-      Surveying
              630-      Structural
              705-      Engineering Geology (Soil Mechanics)
              1501-     Applied Optics
             TC         Hydraulic Engineering
             TD         Environmental Technology
             TE         Highway Engineering
             TF         Railroad Engineering
             TG         Bridge Engineering
             TH         Building Construction
             TJ         Mechanical Engineering. Machinery
             TK         Electrical Engineering
              5101-     Telecommunication
              5105.7-   LANs
              7800-     Electronics
              7885-     Computer Engineering
             TL         Motor Vehicles
              500-      Aeronautics
             TN         Mining Engineering
             TP         Chemical Technology
             TR         Photography
             TS         Manufactures (Production Management)
             TT         Handicrafts. Arts. Crafts
              180-      Woodworking
              205-      Metalworking
             TX         Home Economics (incl. Food. Diet, etc.)
              901-      Hospitality Industry
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        U  Military Science (General)

        V  Naval Science (General)
             VK         Navigation. Merchant marine
             VM         Naval architecture. Shipbuilding. Marine engineering

        Z  Books in General
             Z 52.5-	Word Processing
               105-     Book Industries and Trade
               1001-    Bibliography

             ZA         Information Resources (General)

               4201-    Internet

               4226-    World Wide Web