Default [Q] ebook/epub O'Reilly alternative ebook reader ..

I've bought several O'Reilly books and references, the only thing that irritates me is that this app from O'Reilly is so incredibly sparesome when it comes to features, the navigation is quite awkward and accidentally hitting the back button closes the app entirely.

I'm looking for an ebook reader that is very pleasant and easy to navigate in.

Only requirement is that it should have bookmarks and support epub+pdf .. What would be very nice is if you could navigate to/from bookmarks in one book to another ..

What are some great alternatives out there that are not bloated with functions?

I only use it for reading tech-books (Programming in particular)