Kirshner, Robert P., The Extravagant Universe (Princeton Univ. Press, 2002).
Popular book by a leader in observing supernovae. It discusses accelerating expansion of the Universe.
Guth, Alan H., The Inflationary Universe: The Quest for a New Theory of Cosmic Origins (Addison-Wesley, Reading, MA, 1997).
Quite comprehensive but more advanced book.
Thorne, K.S., Black Holes and Time Warps (Norton, NY, 1994).
Article by Lineweaver, Charles H. & Tamara M. Davis, Misconceptions about the Big Bang, Scientific American 292, no. 3, pp. 36-45 (March 2005)
(mentioned in Geraint's lecture)