This review is based on reading an English translation of Given through chapter 28, the end of volume 5. The scanlator says chapter 29 is not yet available in Japanese.
Minuses (-)
(-) The author repeats a very common BL (boys' love, shounen-ai, yaoi) trope: a male character thinks he is abnormal because he is in love with another male. Japan is many years behind other countries in terms of LGBT rights. It isn't even one of the 29 countries that legally perform and recognize same-sex marriage (see Wikipedia for a list).
(-) Several of the characters' names are unusual. This is awkward. What if calling your friend's name took seven syllables (u e no ya ma ku n)?
(-) Mafuyu only comes to life when he's singing. That doesn't happen very often. Let's hope he sounds good in the anime.
Pluses (+)
(+) Given has a plot, and it's an engaging one. One major theme is how music makes people resonate, or sympathize, with each other.
(+) Very few BL manga are made into anime. Given is being adapted into anime because it appeals to a wider audience than just fujoshi, who might even prefer BL that are all sex and no plot.
(+) It seems that the author really meant to tell the story of Akihiko and Haruki.
(+) The author uses humor very naturally, without distracting from the story.
(+) The drawing is gorgeous. For example, look at the hands. If only other BL authors could draw so well.