Seeing as how many people will check the reviews of the first volume to check whether they want to read a series or not, I'll post my full review here:

Girl Friends was one of the very first yuri manga I ever read (after a year or so of reading VERY questionable yaoi manga) and to this day I can proudly say that it is my very favorite manga series. I love the characters a whole lot and adore the progression of Mari and Akko's relationship over the course of the five books. Book 3 is, in my eyes, the weakest book of the three, but it provides a central point of conflict that was probably necessary so that the two lovebirds can finally be honest to each other. The ending is a very very happy and optimistic one! There are a lot of cliché scenes of "but I'm a girl!/but we're both girls!/wait, women can date each other??/but friends do XYZ all the time and it doesn't matter!", but this seems to be a prerequisite of most yuri manga. Not to be overlooked: the cast of side characters is adorable and hilarious, with most every girl being their very own person and a great source of comic relief when necessary, which isn't always a given.