I've purchased all three editions from LitJoy (Coraline, Stardust, and yesterday's The Ocean at the End of the Lane). They had a limited number of signed copies available and make no mention of how many are actually available. I even pay for the $10 early release membership and never managed to snag a signed copy. Looking at their socials, it seems like there were relatively few available because of just how many people are upset that they couldn't manage to get one.

LitJoy (and all of these other YA collector box publishers) put out an okay product. Very similar to trade editions with new artwork. They're also BIG on digital (aka facsimile) signatures which I'll never understand. They list it as a special feature kind of like how Disney used to say Artwork as a special feature of their DVDs back in the day.