Subetalodge tells me that the above book is in the cash shop. I've looked carefully but cannot find it. Could a kind soul please tell me where it is.

It's in the themed item section near the bottom :)

Saved again by Subeta's gallant knight! Ty <3 I looked right at it but didn't see it. I distinctly remember considering buying the scales next to it for my scaly pet, Millard. Ty v m!

No problem! I did the same thing, went through there and bought a few books I needed then had to go back a second time because I realized I didn't get everything. It can be pretty difficult to see things amongst all the other items :p