Well i guess it depends on how meny discs you have and how much space you have at the end of the day.Any data i want to archive for a long long time i will proberly keep in a cd jewel case, everything else at the mo is in books,I have way too meny discs :).
I did use storage books that hold 240 discs, they was early ones , datawrite branded. But i have since given up on books as the last lot i bought the zips tore out after a while, the discs also seemed to get marked more from the friction as the folder moved about in different directions. I am now in the process of changing my discs over to djstyle case's.
All original audio cds,film dvds and games(pc and all consoles i have) stay in there original case. At least with the backups if the get to badly marked i dont have to buy new i can just re-backup.
@chas0039, i have a 390 discs mirror brand djstyle i did notice the sleves are a tad tight, how have you gone about stretching them out a bit. Was thinking of only using one side of the sleeve but then that cuts 390 storage down to 195.