This might be too advanced for you right now, but maybe its a good read anyway: http://www.amazon.com/Engine-Architecture-Second-Jason-Gregory/dp/1466560010/ref=sr_1_1?ie=UTF8&qid=1418117671&sr=8-1&keywords=game+engine
Pretty much an introduction to everything going on in a modern 3D engine. Good basic knowledge for anyone working in 3D Game dev field, and mandatory reading for everyone trying to write his own engine for the first time, IMO.
If you ask me, every software developer should have at least basic knowledge in HTML/CSS and Javascript. Really, it ain't rocket science, but its still hugely useful for multiple lines of work (Starting with web development, if you go Indie, you might be able to safe some bucks because you can get your website up and running yourself, web game dev also relies on it, AND more and more tools seem to adopt Javascript (-lookalikes, sometimes) as scripting language... Unity as Game Engine, Adobe for some of their PDF tools...).
Mastering the art of juggling different browsers to spit out the same rendered page from your HTML/CSS output is a higher art form, though.