I have written a picture text book for children and there will be around 20 books in the series. I have a publisher that has shown interest, and wants to know whether I want my books to be published as a collection in one volume of work, or for all books to be published separately but at the same time, or for all books to be considered distinctly on their individual merits, potentially allowing time for the first to generate sales. I am new to this so it would be great for someone to give a little advice.
If I think about all the picture books my son has owned, the only ones (that I can think of) that are less than twenty pages are the very cheap, cardboard-page books that we bought from the supermarket for a pound each.
Everything else has many pages.
You really have to talk to the publisher.
Publishing in a volume just means putting more than one story in a single book.