Your publication should be at least 48 pages (plus the cover - covers are usually not counted as part of the page count of a book unless it is a "self-cover" book: ie all the same paper stock, printed on the same signature and then folded and bound together usually with staples ("saddle stitched".) Your books will be perfect bound, and so the cover is printed separately on a heavier cover stock.
BASIC STRUCTURE OF A BOOK
FRONT COVER
Left hand page: inside front cover
Front Matter:
Right hand page: half title page
(page numbering/counting starts on this page)
L: title page
R: title page
L: copyright page
R: table of contents
content pages
back matter:
appendices if necessary
bibliography if necessary
index if necessary
colophon if necessary
inside back cover
BACK COVER
As you can see, the structure of a basic book will take up quite a few pages, so you may need to increase the page count of the book to allow for your content. When considering the final page count, keep in mind that you cannot just add a single page; books are printed in signatures in multiples of 4: usually 16 or 32. Digital printing may allow you more flexibility in the final page count, so consult with your production house.