But now, according to Publisher's Weekly, they are now available. I will certainly have to check this out.
"Animals real, mythical, and imaginary headline Stephen Cosgrove’s Serendipity series of picture books, which is currently being reissued by Clovis, Calif.-based Heritage Builders Publishing. The 72-book series, originally launched in 1974 by Serendipity Press and out of print for a number of years, has sold more than 80 million copies worldwide. Illustrated by Robin James, these paperbacks offer stories addressing common childhood experiences and issues, including friendship, disabilities, fears, prejudice, and the environment.
Heritage Builders, whose books are distributed by PGW, released the inaugural eight Serendipity titles last January, and four more books followed in August. Four additional reissues – Kartusch, Squeakers, Trafalgar True, andZippity Zoom – are due in October, and three installments are scheduled for spring 2015." (PW, Sept. 9, 2014)