The Allegory of Love is a scholarly book, but I think it can be read with enjoyment by anyone interested in medieval poetry. The first two sections discuss of courtly love and allegory. These sections are primarily theory. If your main interest is the poetry, I believe they can be skipped with no diminution of understanding. Lewis, in fact, doesn't make use of them in much of his analysis of the poetry. The major area where he sticks close to them is in his analysis of the Romance of the Rose by Guillaume de Lorris. Here understanding allegory is quite important although Lewis gives the relevant overview in his analysis of the poem.
The next sections discuss the poems from the Romance of the Rose, through Chaucer, Gower, some of the lesser poets, and Spencer. I found his analysis enlightening and easy to understand. My favorite chapter was the chapter on Chaucer. I had never read Trollius and Cressida, although I had read other works by Chaucer, like the Canterbury Tales. I found Lewis' analysis of Cressida very compelling and psychological. For me it was worth the whole book.
Some attributes of the book that will be hard for the general reader. Lewis uses Greek and Latin words in chapters one and two. He doesn't translate the words or all the passages he cites in Latin. He also uses the old English versions of the poems, which can take some thought to decipher. Still, I found the effort well worth it in understanding medieval poetry.
Although much of the writing is scholarly, Lewis' humor peeks through. I encourage you, if you're interested in medieval poetry, to not be put off by the scholarly. The analysis of the poems is extremely well done and well worth reading.
I reviewed this book for the Amazon Vine Program.