Does Rick cover Malta in any of his travel books? If yes, which one?
Why not just get another book?
If you even need one--the tourism website was one of the more helpful ones I have ever used: https://www.visitmalta.com/en/
DK top 10 Malta; we have a whole shelf of DK pocket guides
Rick Steves guidebooks are unlikely to covers countries if he does not have tours that visit those places.