Located under 'Player>Books>Compendium of Love', this book allows you to track how you can breed specific species in the Breeding Shop.
If you have not discovered a combination yet, hints will be displayed for what is required to breed a creature's egg.
You will receive a confirmation message in the breeding dialogue when you have successfully discovered a new combination. Complete as many entries as possible and you might just unlock a particularly sexy Soul Puppet.
Breeding hints were written in a colaboration with the following players: