I'm a huge Tolkien fan, so last year I got his translation of Beowulf, but I'm not in a good position to rate this book. For whatever reason, while I consider myself a reasonably avid reader, I hadn't previously read Beowulf. As a result of not having read it before I really can't say if it is a good translation or not. 
 There is the translation, then Notes on the text of the Translation, Commentary, Sellic Spell, and the Lay of Beowulf. 
 Beowulf as a story is enjoyable, reads well, and provides some potential insights into the impact on Tolkien's own works (dragons, evil, treasure stealing people, kings, honor, warriors), but I can't say if it is better than other translations or not. 
 For academics, I would imagine the notes on the text of the Translation would be interesting, but for me, not so much so. I couldn't read through them. The same was true for me relating to the commentary on the translation. 
 The Sellic Spell is a work of Tolkien's based on Beowulf and a final and original version are included. 
 The Lay of Beowulf is also a work by Tolkien and similar in what he did with the Lays of Beleriand retelling his own stories of Beren and Luthien and the Children of Hurin in the Lay style.