Hello Aspirant,

Computer science is a foundation science and its subjects will vary at different levels like high school,graduation and masters.Since you have not mentioned at which level you are asking for I am providing a general answer with a list of all possible subjects that come under computer science . Just to mention, the most important basic subjects you will come across in any computer science program are data structures,algorithms,discrete mathematics,systems,architechture,computation model,software engineering and design.

Below is the list of subjects:

Discrete Mathematics--- Algorithms---Programming and Data Structures--Software Engineering---Switching Circuits and Logic Design---Formal Languages and Automata Theory---Operating Systems---Compilers---Foundations of Computing---Computer Organization and Architecture---Theory of Computation---Computer-Networks---Symbolic Logic and Automated Reasoning----Principles of Programming Languages----Symbolic Logic and Automated Reasoning---Artificial Intelligence---Electronic Design Automation----Image Processing---Applied Graph Theory--- Computational Geometry and Complexity--- Advanced Computer Architecture---VLSI System Design----Multimedia Applications---Microprocessors and Microcontrollers---Digital System Testing and Testable Design---Database Management Systems---Distributed Systems---High Performance Computer Architecture----Logic for Computer Science---Database Engineering---Embedded Systems---Testing and Verification of Circuits---Cryptography and Network Security---Advances in Compiler Construction---Real Time Systems---Advanced Graph Theory---Theory of Programming Languages---Machine Learning
--- Low Power Circuits and Systems---Speech and Natural Language Processing---Object Oriented Systems---Formal Systems----Multimedia Systems--- Advances in Digital and Mixed Signal Testing---Complex Networks---Information Retrieval

Now regarding the best books to refer,if you are asking generally,then you may search them on the internet.On the other hand ,if it is for an entrance exam or a college degree then accordingly you may visit the official websites to see the list of prescribed textbooks or reference books. If it is for CS engineering then you may visit the below link to books for GATE CSE, this exam is a popular exam, hence these books would be useful at all levels:

https://www.google.com/url?sa=t&source=web&rct=j&url=https://engineering.careers360.com/articles/what-are-best-books-for-gate-cse/amp&ved=2ahUKEwju7pzF_ITuAhXayDgGHdlnAEEQFjAAegQIAhAB&usg=AOvVaw2vz1agd6gYhnjvCgOp5f3K&ampcf=1

All the best