Introduction to Cosmology by Barbara Ryden is perhaps the best book to introduce someone to the subject. After reading Ryden, what books should a student who's interested to pursue research in cosmology look upon? Is Cosmological Physics by John Peacock a good option? There are some negative reviews of the book though. I personally think the book by Peebles is a little bit old fashioned and disorganised. Modern Cosmology by Scott Dodelson maybe a tough read for someone who has read only Ryden.