What CS Textbooks should I buy?
For Computer Science, I would recommend you 


  Computer Science: An Overview 11th J. G. Brookshear. 


If you are more interested, you can attend one of the online courses, you can register for free and finish these courses online with exercises. I recommend you one of these: 


An Introduction to Computer Science from Harvard, more informations you can find here EDX
Computer Science from Stanford, more info here


Algorithms, you can find relevant online courses following these books on EDX and Coursera as well. Depends on how much time you have and want to spend on these subjecs, and how deep you want to go. 


  Algorithms (4th Edition) by Robert Sedgewick and Kevin Wayne


or 


  Introduction to Algorithms by Thomas H. Cormen, Charles E. Leiserson, Ronald L. Rivest and Clifford Stein