Eli Bendersky's website I'm absolutely committed to reading all of Sagan's popular science books, so I picked up "Broca's Brain" although I have already read some of his newer works.
Broca's Brain is a collection of essays on various topics, dealing mostly with Sagan's main speciality - astronomy, astrophysics, speculations on human future in space and on extraterrestrials. He presents some of the recent (for 1975) findings in these fields and much of the material is basis for his later (and far more popular) work - Cosmos.
There are also a few interesting digressions - one a short biography of Einstein, emphasizing his philosophy regarding science and religion. Another is to dispute a then-hot issue of the "catastrophism thesis", by one Velikovski. While I wasn't familiar with the issue (that was probably popular 30 years ago and forgotten since) I really loved Sagan's rebuttals - pragmatic, scientific, poignant and at times funny.
Although it's not one of Carl Sagan's best books, I did like it. It's work spending a few days on the book even for a few examples of Sagan's thinking and approach to life and science, which is a true inspiration.