For the knowledgeable and the loving
Yes, I would recommend it, but to those with a viable knowledge of musical theory. If you don't understand the ins and outs of composition, you may love Mendelssohn enough to persevere through this long, insightful, detailed account of everything he ever wrote. It will, however, take an amount of concentration, not to mention dedication. It seems to me that this remarkable study rescues the composer from the dust bin of superficial criticism that has buried his tremendous output under dismissals of his work as sweet and sentimental. It also gives you a very living sense of who he was, his background, his religious sensibilities as a profound Protestant interpreter of the Bible and a respectfully ethnic Jew.
Mendelssohn seems never to have wound down. Only when seriously ill did he stop--temporarily. His wife, fortunately, seems to have been the calm and quiet type. It is fascinating to imagine him with the Schumanns, Paganini (who gave him the willies) and others of that magical time. You wonder about the further implications of the psychological interdependence between himself and his sister, and his unwillingness to let her publish her own music. One of those fantastic prodigies, in the line of Mozart and Saint Saens, he remained a Golden Boy during his lifetime, and died too early.