It is surprising that lots of people(including me) learn about this book only now[1]. Have you read any other book like 'Calculus Made Easy'? Please mention in comments. Not only in maths. It could be in any subject or field. I think it will be helpful to many.
[1] https://news.ycombinator.com/item?id=14161876
If you go through that one, give Calculus by Spivak a try. Interesting book and starts off with a bit more of the fundamentals.
How to solve it by Polya - an awesome book. Read these to learn not just mathematical problem solving but in general. I don't think I've read a book quite like this before. The idea of a process and tools for problem solving is awesome.
How to prove it - a great book. I felt after reading through this I had a much better understanding of how proof works. I also had a better understanding of how mathematicians go from scratch work and proof to the proofs they finally present. There's a lot more that goes behind them and will help you understand those proofs by giving you the tools to do the scratch work behind them yourself. I had tried to learn proof techniques from a few other sources, including Jeremy Kun's awesome primers.
"Conceptual mathematics" - did a very good job in helping me make more progress with category theory. I tried a few different books and an online series. Flicking between those and this book, I started to understand much better.
The Little Schemer - the one that finally opened the key to recursion, closures and functional programming. I had tried attacking this using a few other books, including SICP but TLS helped a tonne in the final clicking.
Thinking in Type - great book that taught me quite a bit about typography. It showed me how important typography is to design.
You can draw in 30 days - sounds very SAMS but actually​ the progress I made in 1 day is testimony to the book's bold claim. You won't be Da Vinci but you will have functional drawing and sketching skills if you go through this.
It's important to note my process in finding these books. I think much of the groundwork and mental priming before working through most of the above helped a lot.
A tend to get interested in a topic and then seek out good books in that field. If the book doesn't make much sense or is very dense, I keep at it for a day or so. I then seek out similar books and repeat the process until a little jump forward.
Unfortunately in around 1 to 2 weeks, I've lost interest and I repeat the same thing on a different topic.
I probably have a tonne more but they're spread across many subjects so it's difficult to consolidate. Feel free to email me if you want recommendations for a particular subject.
I think But How Do It Know?[0] is a good read. It takes a similarly straightforward and light-hearted first principles approach to computer systems organization. Highly recommend.
An oldie but a goody for a curious mind needing a base for learning electronics. The handwritten text & drawings made the task of learning seem slightly less daunting, IME. That was 30 years ago, and yet I still see the smiling electrons in my mind`s eye when problem-solving transmission issues on-board and on the network.
It's kind of outdated now. But Mastering EJB (2nd edition) by Ed Roman was very helpful to me to understand EJB at one point. The writing was very different from a typical technical book. It was like reading a novel.
The one that immediately springs to mind is "Mathematics For The Million" by Lancelot Hogben. I really enjoyed it because it places mathematical developments in their historical context.
CODE by Charles Petzold and The Elements of Computing Systems by Nisan and Schocken
If you want to know about how computers work, I would recommend books written by Anthony Dos Reis[0]. I could say that all of his books were very easy to read and follow. I learned tons of stuffs from his books like assembly language, computer architecture, writing an assembler, creating a CPU simulator, know how compilers generate machine instructions, know what are grammars, formal languages and learned how to build a programming language, write a recursive descent parser, incrementally improving a compiler, implement grep after learning automata theory and a lot _more_ cool stuffs from his books. Those books were the reason why I got hooked with computer science. I just got his new book about abstract algebra which had been released last month. There's a lot of gems on it and I'm still reading it mostly it could take me months to finish reading but it really had gave me quality time grokking the concepts. I never meet this man but I owe so much from him and hope there would be more books that he could write like about operating systems.
[0] - http://cs.newpaltz.edu/~dosreist/