Having seen a few examples of books you never thought would be published (you will find some on here such as these, these, and these), I think I finally found the answer in the works of Bob Staake who designs retro looking book covers with  very amusing titles.

His Gallery has a full set of Bad Children’s Books and as a teaser, my two favourites are below :

The rest of his gallery is well worth a look for some highly amusing book covers.