Among biographies of CS Lewis, this is - with its companion volumes - the longest, and both its merits and demerits come from that.
Positively, it is thorough. The enthusiastic reader who has read all of Lewis' main books and a decent portion of the letters already knows almost as much as some biographies tell. This immerses you in a far wider selection of sources - particularly letters by Warnie, Kirkpatrick, and Albert Lewis - that give a much better and more rounded picture. In this first volume particularly, the way it steps you through Lewis' formative reading, both educational and recreational. There are great anecdotes and quotes from Kirkpatrick in particular. The author is determined to show that biographers need to put greater stress on Lewis' earlier life in order to understand him; he's certainly not wrong that to understand Lewis you do need to know his childhood.
And yet... this is such a repetitive book! It's very oddly structured. The author is so determined to prove that a detailed exploration of his childhood is important, that he keeps on bringing in discussions of episodes from Lewis' later life, or discussions of his books, in a way that seriously detracts from actually telling Lewis' story. What's still worse is that these digressions are incredibly repetitive - each time Poe returns to a particular book of Lewis, he will mention the same anecdote again. And why does this book end by stealing the thunder of the next volume, giving a substantial account of Lewis' conversion? At times it felt the book simply hadn't been edited.
Indeed, the book slips into a habit of finding a relation between every single experience of his childhood and every single aspect of his later work that is rather tiresome. Considering Lewis' own writing against 'The Personal Heresy in Literature' this seems bizarre. Some links are plausible - Lewis, who had been a young boy with a dying mother may have been drawing on his own experience when he wrote about Diggory in the Horse and His Boy. But the confident assertion that the woods of Narnia are based on the woods of Surrey, since that's where Lewis went walking as a teen, is laughable... it's not as if his beloved medieval romances lacked woodlands!
One of the main merits of the book, besides its readability, is that it brings out the nastiness of young CS Lewis better than most other biographies. Though Poe does slip into hagiography quite regularly, he does cover his deception of his father, his flirtation with sadomasochism, his arrogance, and other unpleasant features much better than some other authors. This helps highlight the transformation that really did come when he was converted.
That makes it all the more peculiar that here (and in the next volume) Poe can cover the liason with Janie Moore in such lurid detail - the hidden stays with her, the secret holidays, even the way in which his family took comfort from her still-married state because it meant that he couldn't marry her - and yet conclude that the relationship remained at most adolescent attraction and was ultimately platonic... that they lived together only because of his chivalrous vow to look after his friend's mother. Poe wrote the first two volumes before the posthumous release of Hooper's interview which confirmed their affair, but it really does seem as if Poe is blind to an awful lot of evidence, as well as the assertions of other biographers.
All in all, this is a worthwhile read for those seriously interested in Lewis, but more because it regurgitates a lot of archival work than for the judgements that Poe makes. His conclusions, and his descriptions of how every book Lewis ever read came out in the books he wrote, can comfortably be skimmed.