The original children's historical fiction picture book was self published by the author. It sold a few thousand and was on Amazon but was too expensive to continue being published by the author's publishing company that she established. We (I'm the illustrator) would like to find a publishing company for the first book (how America became a country) and the second book in the series is finished with illustrations (America's westward expansion). How do we write up a query or submission for both books in the series? We have published copies of the first book, manuscripts and original illustrations for both books. Looking for advice. Thanks
This is a tricky situation. Generally, traditional publishers don't want to republish a book unless it has been a significant success. The (non-scientific) rule of thumb I use is that 3000 sales of a previous title is enough to use it as a legitimate writing credit. But in order to make it a hot-enough property that the publisher will want to re-release this book, you'd probably need sales in the tens of thousands of copies.
Therefore, I'd recommend trying to sell the new book as a stand-alone, using the success of the previous book as a writing credit.
With that said, I'm not sure why it would be expensive to keep your previously-published book in print independently. EBooks cost nothing to keep in print, and even short print runs start around $5/copy these days for legitimate POD printers. (It might not be worth it to sell print on Amazon, but you could print up a box and sell it at local author events for a tidy markup.)