Reddit reviews Over The Garden Wall: Tome of the Unknown

A good place to start is with this book, which contains both the special and the 4 part series. These particular comics are most connected to the show, because the first four take place between certain episodes. The fifth and final comic in this book sheds some light on the Woodsman and his daughter. These were all written by Pat.

There is also the current on-going series, which takes place after the show and follows a whole new story. The 13th issue comes out on Wednesday. If you want to catch up, your best bet is probably going to be with digital copies. For future physical copies, you can find them at a local comic book store.

Well the most obvious recommendation would be the plethora of OTGW stuff that's been released since.

If you haven't checked it out yet the original short is available online, right here on youtube.

The first comic collection has stories from in between episodes, and I believe is cannon.

Since then, there has been an ongoing comic series. These contain stories from after the show, the longest thread being Greg and Wirt's adventures in their dreams. However there are also stories about Anna (the Woodsman's daughter), Mrs. Langtree, and others. The first few collections are available on amazon.

Lastly, a concept art book is about to be released, if you are interested in that sort of stuff.

Hope some of this helped!

Yup! There are two different series, and I believe you can buy them both as ebooks:

A limited run written by Pat McHale, which fills in the gaps in the canon series with new stories. Issue #1 is an adventure taking place directly before Tales of the Dark Lantern is set. Issue #2 is set right before Mad Love, and is a comprehensive look at Fred's backstory and his relationship with the Highwayman, as told by Fred to Beatrice/Wirt/Greg. Issue #3 is another adventure in which we see a bit more of Beatrice's perspective and guilty conscience. Issue #4 is Anna's backstory.

The second series is ongoing (you can buy a subscription as well as the previous issues on Comixology). Half the adventures take place post-canon as Greg (and later Wirt) wind up in the Unknown when they're asleep. The other half of the adventures are Anna's life at home on her own, meeting the ghost of her mother among other things.

There are also a few issues in there so far illustrated by George Mager, which are tales of Langtree's classroom written picture-book-style.