Penguin 75? More like Penguin 10, since the book only covers the period 2000 to 2010. It's attractive and nicely produced, and provides some interesting insights into the design process, but I'm disappointed that there are no covers from the period 1935 to 1999 - a bizarre omission for a book that claims to be "a celebration of the 75th anniversary of Penguin Books". Another thing to be aware of is that it's produced by Penguin US, and so focuses on covers of the American editions.
Good if you're interested in modern book-cover design (especially novels). Bad if you were hoping from something similar to Penguin by Design: A Cover Story 1935-2005 but with a more in-depth look at the origins of each cover.