Yep, BOL uses epub (as do pretty much all vendors other than Amazon, though you can convert books to other formats), so you ideally want an epub reader. As mentioned, I feel that the Kobo Aura for €99 has no competition in that price segment. I feel it is under-priced.
Manga, and anything else in PDF format, you can pretty much forget on any e-ink reader. It works, but it is slow and sluggish, and just not much fun. For PDFs, you'd want an iOS or Android tablet (Nexus 7 would be the cheapest quality option here, but that starts at €220 or so). For reading books, an e-ink reader is nicer.