What's the Name of That Book??? discussion

When I was in ninth grade I ordered a book from a scholastic catalog and I can't remember its title. I think the year was 2003 and so the book was probably published around that time. It was quite thick and involved a bunch of cats who made a journey down to an underground cave to visit a fat and morally corrupt cat king. At this point the book got a little gory and I remember my conservative 9th grade self being a little shocked. (haha) I think he was eating the other cats or something? I believe the cat king was somehow defeated and book ended with cats living on an island with a lighthouse.

I have searched for this book many times on Google because it was one of the first fantasy books I ever really enjoyed. If anyone could help me find the title, that would be awesome! I know I'm not giving you a lot to go on though.

I think the cover had a picture of a fat orange tabby cat.

What about Tailchaser's Song? It ends with them discovering a horrible cannibal cat underground.

I second the suggestion for Tailchaser's Song.

It is indeed Tailchaser's Song. Thank you so so much for helping me find this book! :) You guys are awesome.