Since there are two people already recommending JadeGarden I'd say if you liked it another good read is Jade Route
Very different though, a much more experimental approach in the comicking and more focused on HSBC

I haven't read it in a long time, but I remember liking Detective Pony
It delivers on the premise of Dirk having written Jane a customized copy of Pony Pals:
"And then there's a customized copy of PONY PALS, a gift to you on your 14th birthday from the slippery Mr. Strider. Each page contains lovingly hand-written commentary on the deeds of this intrepid young horse. Later, about halfway through the book, rather than see the gag through to the bitter end, Strider began pasting over entire pages of original text with his own completely rewritten version of the story, while keeping all the chapter titles. His revision is a tough, emotionally draining read. But it's cathartic, in all the worst ways possible.
He tends to get carried away with his projects."