Well, it's not a book yet, but that diary with all the excellent animal illustrations is going to good use. I made up a set of A5 sized pages, and did a starter collage on each one (punched or torn bits of old text pages, then gesso and paint).
Then I started adding creatures, and whatever else the pages seem to need. Haven't finished any yet, but here's some interesting progress.
The edge of a foam block (one of those ones you can heat form and make a stamp - we get them from Reverse Art Truck, and now from Resource Rescue) makes a great paint smearer. I was really liking it there. And also just right as a "stamp pad" for when you want to stamp with paint. Which of course you must wash up right after!