Hi, M3lchior!
Like you said, poker world is evolving so fast and to be honest, I think the most common educational materials to be found nowadays are videos and articles. Harrington had 3 books on tournament poker and I remember back in the days, I thought they are good. However, if I compare it to how poker has developed since then, it looks ultra outdated and nitty. Some conceptions about ICM are also wrong imo.
Another example would be Collin Moshman SnG strategy. I remember I read it back in late 2010 and it helped me a lot. It's a really good book by a truly talented player and coach. However, it is still dated to our days standards.
To answer you shortly- my advice would be to read the articles on our site(some of them already got updated to be more helpful and precise) and watch many, many videos. From 2012 and on. Also, I found the hand evaluation forums very helpful. Always work on your game, watch new videos and post/discuss hands with poker buddies or in forums.