What have I learned? Very much, indeed. The fact is that these books are carefully written, extensively tested and proved to be actually valid in most scenarios. Although people tend to consider paper books as obsolete, I think that it's still quite relaxing lying in the bed before falling asleep with a good book to read. By doing so, you can dramatically increase your level of technical background with a minimum effort.
Generally speaking, these books are written in a very simple language, full of examples (not to mention the downloadable code that comes together with each publication) and with a step-by-step approach. It's also worth mentioning the fact that authors are always great developers (Eric Meyer, John Resig, Nicholas Zakas, just to mention few) with a strong technical background and a vast working experience.
So here's a little piece of advice: read! There's nothing to lose and everything to learn.