I read and mostly enjoyed
Medicus (it was a first novel and had some flaws; my
non-spoilery commentary over here if you're interested) and got the 2nd via Kobo while it was 99 cents. But then, I have this fondness for ancient Roman stuff and amateur sleuthing, so your mileage may vary if that's not a strong draw for you.
And I will say that even so, I would have probably not paid the 8.25 regular asking price for the sequel and opted for the library option instead, at least until I'd tried a few more books in the series to decide if they were really worth shelling out for.
Anyway, free NOOKcolor book which hasn't been posted to this thread yet:
Fun Facts About Pets, by Seymour Simon, a children's picture book
Also, Wednesdays-only for the month of February, DRM-free ePub & PDF giveaways from publisher Carina Press, free with coupon from their website.
This week,
Silver Bound sci-fi romance by Ella Drake,
see this thread for details.