Mastering Emacs by Mickey Petersen.
I can’t recommend Mastering Emacs as lite beach reading but next to a computer, it has few if any equals.
I haven’t ordered a copy (yet) but based on the high quality of Mickey’s Emacs posts, I recommend it sight unseen.
You can look inside at the TOC.
If you still need convincing, browse Mickey’s Full list of Tips, Tutorials and Articles for a generous sampling of his writing.
Enjoy!