Long time lurker here, great forum
I recently spoke with Rolf and his book is due out in October.
As far as books on Limit Omaha 8, The tenner/krieger book is a great place to start, Cappalletti's book is for a more seasoned player looking past starting hands and drawing to the nuts only, hi/lo split poker for advanced players is for tight aggressive games (something you will rarely see at low or mid limits), the ciaffone book has a short section on limit O8 (about 15 pages) good advice but really what can you explain in 15 pages
I think the best info on the game is on Steve Badgers website. Couple that with the tenner/krieger book and you'll do pretty well. Just avoid their starting hand advice and stick to A2 A3 handswith a few exceptions.