Dan has a bunch of book recommendations ,at the bottom of his home page, here;
https://www.motionscript.com/
The only one I have of those is,
Creating Motion Graphics with After Effects, Volume 2: Advanced Techniques
by Trish and Chris Meyer
but it’s great for expressions, lots of examples and a bonus chapter with lots of aep’s, highly recommended.
I presume you know about these two sites, also:
https://jjgifford.com/expressions/basics/index.html
Lots of good basics.
and here:
https://www.aenhancers.com/
Hopefully Dan will write a book someday, but until then just do an advanced search here at the Cow with his name for Author and go to the Archives as far back as you can, it’s what I do when I have time to burn, he’s written many scripts and explains a lot of them. Enjoy.