first of all, thanks for creating this Screensavers Hack. it works well generally, but they are a few issues which i hope you can look into.
i'm not familiar with how book covers are stored in mobi files (in fact, i'm confused by it), but i realised that each mobi file can have 2 covers or more(?). anyway, i found that when there are 2 covers, the one used by your screensavers hack is different from that used by JBPatch's cover patch. not sure if it will be a good idea to use the same cover.
i also encountered in one instance when the cover couldn't be shown as a screensaver. investigation revealed that, the book had 2 covers build-in (the extra cover only showed up when i read it with Calibre's viewer, but not Mobipocket reader). only after i've removed the extra cover using Calibre's convert books function, then it was able to show up as a screensaver. would you consider modifying your hack to take into consideration this situation? thanks again for your great work.
ps. just to show you why i'm confused by the way book covers are stored, for eg, when i viewed the metadata of Alice in Wonderland, there's a cover which is different from the one show in JBPatch. if i add a new book cover, screensaver hack will show this new cover.