Books not displaying as they should

Okay, I'm having a hard time understanding why Calibre doesn't display my books as-is--rather, what I see in the thumbnail isn't what I would get, and I would greatly prefer to view my books the way that the publisher intended, rather than what I'm seeing, which I think is Liberation Serif. Someone in another forum speculated that Calibre may have converted all my books in advance. This isn't true, because, when I access my books in the Calibre library from another book reader, such as muPDF, the books display just fine; however, whenever I open a book from my Calibre library, it takes a good minute until Calibre actually displays it, so I suspect that calibre is in fact sort of converting the books when they are displayed. Looking in my Calibre library, Calibre only maintains one copy of the book, and that's the vanilla version, though.

Here's an image to make things clearer:

Edit:
Okay, I just noticed that there was a settings prompt in the toolbar while displaying the book, and in that window, there's a bunch of prompts under "Font options". When I change this options, they modify the text being displayed, which makes things a little bit more manageable, but what I would really like is to get rid of these modifications altogether and just read the darn book as it was supposed to be read! Why is there no way to toggle this?