
Applications of No-Limit Hold 'em, by Matthew Janda - this one goes into specifics about how to think on each street, how to build a good strategy etc. Some of the details will be different from the latest theory because the book was released in 2013 but it's still a very solid read if you want to level up.
This is the journey I would suggest for someone starting out:
1. Johns Hopkins Poker course[0]. Taught by a CS professor who's very passionate about Poker. It's targeted at college students and it's very well explained.
2. There are two different MIT Courses. I thought that 2016's [1] was better than 2015's [2]. But 2015 has better guest talks. "Poker Economics" and "Decision Making" are must watch.
3. Matthew Janda's books "Applications of No-Limit Hold 'em" and "No-Limit Hold 'em for Advanced Players" are both really good. They take a theoretical approach to the game. Applications was written before good poker computers were common. The author goes very deep into all the thought process and things you want to balance when playing.
NLHE for Advance Players runs common situations through strong bots and abstracts away good strategy principles that you can apply at the table. It's a lot easier to read than Applications.
4. Another good book that covers some of the math and optimal opening ratios is "Modern poker theory". It's more focused on showing charts, ratios, understanding the math. It also has good principles but Janda's books seemed easier to put in practice.
5. There's also some really good seminars on Jonathan Little's channel. "Play more Aggressively"[3] is particularly interesting.
[0] https://www.youtube.com/channel/UCBYvo69VZ2Gl3ZtdPmcsW9Q
[1] https://www.youtube.com/watch?v=62nDLA_A8gs&list=PLUl4u3cNGP...
[2] https://www.youtube.com/watch?v=OTkq4OsG_Yc&list=PLUl4u3cNGP...
(This, in addition to what the other comments have said about there being spots where a bet can get better hands to fold with some probability AND get worse hands to call with some probability - see the chapter "The grey area between value betting and bluffing" in Applications of No Limit Hold Em)