Complex sentence: Though the book promised that any other ways of saving money would be accepted as a submission by the publishers and printed with a credit in subsequent editions, the book is long out of print, though it may be found in used-book shops.
Split into simpler sentences: Though the book promised that any other ways of saving money would be accepted as a submission by the publishers and printed with a credit in subsequent editions. The book is long out of print, though it may be found in used-book shops.