To give items to ghosts, you need to place the items in front of their graves! Interacting with the grave from the front and selecting the rightmost icon will auto-place the item where it needs to be. The green/pink ghost is supposed to be hard to understand, it's related to the reasons they died and their story has more context clues! As for the problem with losing the book - items can clip through (some) objects, such as the gravestones, at the moment. In the version you played, dialogue took priority over item interaction, which could result in dropped items becoming inaccessible. The priorities should be fixed in the update I just uploaded, so you shouldn't be able to lose items anymore! Thanks for letting me know about that!
Ghasty (the main character) is a snail monster, not just a snail! They wear boots specifically so that they don't track slime around the house ^^ They're also not a ghost - a medium is a living person who can communicate with the dead! The ghosts aren't visible to most people in the town! But thank you for the suggestions, and I may keep a slime trail in mind for some future cutscenes/events planned :D