Simply fascinating.

Be a dear and finish it as soon as possible, if you wouldn't mind.

I appreciate your integrity, %PCName. For a moment, I thought you would just peddle the book for some paltry sum. Here, I have some more reading material for you if you're interested.

Have you already finished studying the book, %PCName? If so, please return it to me.

Come back when you find it.

Let me see. Oh, what a find! The power just radiates off its pages. You've been quite useful so far, so you I'm giving my permission to keep the book for the moment and study it. Remember to tread carefully, %PCRank -- immense power always comes with a cost. Return the book to me once you're done. Enough of that, though. I have more chores for you.

Did you find the tome?

The Daedric Septis is a tome of immense magical power, written by Mehrunes Dagon's warlocks. It's said that Lord Dagon himself taught his followers the vile curses which you can find in its pages. Sounds like a lovely read, doesn't it? I've tracked the tome to the daedric shrine of Rasdamassilu.