I've been using Mantano's Bookari Reader and lately Google Books (or whatever they call it). Not sure if either would accept collapsible text.
Just on my way to work now, so I'll have to check back in here later and give things a better look.
Thanks for the quick reply, guys! I left a similar question on StackExchange 17 days ago and it's had 43 views (a bunch are probably me) and no replies. Overnight here, I've already got two.