I highly recommend this for anyone (younger or older) who likes the MLP:FiM cartoon show or other modern MLP:FiM comics.
This is the 5th through 8th issues of the comic compiled into a single graphic novel style book, and it covers the entire "Nightmares" story arc. It is an excellent choice for someone who, like myself, prefers to read these stories as a single whole book rather than as separate comic issues.
This story is slightly more action-oriented and a bit darker in tone than the cartoon show normally is. It is still appropriate for children who watch the show, but the slightly higher stakes give a bigger sense of danger than the cartoon typically does. As a result, I think this is an especially good choice for anyone who is interested in seeing the ponies involved in a more serious adventure and more perilous situations. However, there are still plenty of humorous and silly moments in it to lighten the mood from time to time.
If you like Friendship Is Magic and want to see more adventures in Equestria, I recommend this product for you. And be sure to also check out Volume 1 if you haven't already.