To Say Nothing About the Dog by Connie Willis is available on bn.com for $1.99.
This is the second book in Ms. Willis' Oxford Time Travel series but can be read first (as I did). This is a great introduction to her 'trilogy-in-4-books' and the most irreverent.
If you are interested here's the link to the book:
The Doomsday Book, the first in the series and two-book set Blackout and All Clear are also very good, but somewhat more serious. Ms. Willis is a great story teller and builds suspense as the narration moves back and forth between current events and the travelers in the past.
Her 'time-travel' rules are coherent, consistent and not overly mathematical or technical. I think of these more as historical fiction than science fiction.