It is a little difficult to categorise this book since while in part it is an autobiography, Lewis goes to great pains to exclaim otherwise. One could also suggest that it falls into a category of Christian literature known as a testimony: a story that is told by the author as to how they became a Christian. However this particular book sort of does not follow the two forms that that type of literature takes, which are:
1) I was a really, really, really bad person, but then God came along and now I am not; or
2) I became a Christian and this is how God has had an impact in my life.
As I have suggested this book does not necessarily follow either of these forms because while it is closer to the first form, normally the writer of that style of testimony goes to great pains to emphasis how bad and evil they were so that the contrast of their current lives acts as evidence of God having worked in them (and the problem with that form is that the author tends to spend so much time emphasising their bad aspects, they have have little to no time to outline how God has changed them, as well as the statements about how they have changed being quite subjective, and as such need to rely upon other people as references to their changed life).
The reason that I suggest this this particular book differs from the standard testimony is that Lewis does not emphasise his wickedness, and in fact he does not seem to suggest that he really was all that wicked – or at least no less bad than the next person (for as the Bible says in the book of Romans: all have sinned and fallen short of the glory of God).
So, the question that is then raised is what is it with this book and what does it teach us about its author. Well, what I would have to say is that in a way it takes us on Lewis' journey through life to that point in time when he came to discover the joy of life, and in another way it also chronicles his intellectual development through not just his learning and his reading, but also through his life experiences. From what I discovered from this book, it appears that Lewis was one of those 'large' boys that is always picked on at school because while they are large, they are not necessarily strong, nor are they all that popular. We also learn that C.S. Lewis was in the trenches for the last part of World War I and came to experience the nature of war first hand. However, while he does state 'this is war, this is what Homer wrote about' I get a completely different idea of war from his description: modern warfare was nothing like the warfare of the Ancient Greeks in that the war Homer describes is a war where the fighting is not only up close and personal, but it also has the generals and leaders getting into the thick of the actions. In contrast, there was nothing personal about World War I; in fact it seemed that the entire war was the end point of industrialisation in which it was little more than a machine that simply existed to destroy people in the most bloody and painful ways possible.
His story about his time at Wyvern (which when I first read the book, I believed it was a name that was made up so as to protect the guilty, but I have since, after quickly performing an internet search, discovered otherwise) is also quite interesting as he seems to pull the cover off what goes on in these exclusive English Public Schools. Mind you, I have never been to a boarding school, nor have I studied at a boys school, so I am unable to authenticate whether there was homosexuality going on between what Lewis calls the 'Bloods' and those known as the 'tarts'. However, it is interesting to note his comments on the topic as I do not believe it is mentioned elsewhere. However, let us take note that:
1) It occurred in Edwardian England, and enough for it to be noticeable;
2) If you were caught it would result in gaol time;
3) Lewis does not seem to think that the reason people do not like it has anything to do with any Biblical prohibition but rather because of its criminal nature, and anybody that is caught in a homosexual relationship is no doubt going to be treated the same as anybody else committing a crime;
4) Lewis believes that there are much greater sins that are accepted and does not understand why it is that homosexuals are punished while proud and greedy people get away with their actions;
5) He does not believe that he has any right to comment on it or speaking out against it.
After Lewis returns home from war the book, for some reason, seems to drift into some sort of esoteric form of writing as he outlines how he meets believers at Oxford (including Tolkien) and how he fights and riles against Christianity only to, in the end, reluctantly concede, at first, that there is a God, and then, as he begins to investigate spirituality, comes to accept that Christianity is the one religion that he can call authentic. In a sense the joy that he comes to discover through Christianity is a type of joy that he had not encountered elsewhere, such as the joy of reading a good book, or the joy that one gets out of pleasurable activity. In fact, as Lewis suggests, humanities desire for pleasure arises from that desire to find joy and to fill oneself with that joy due to the fact that one's life seems empty without it. It is not that pleasure gives joy, but rather it creates a short terms satisfaction that must be continually met because once the initial rush has worn off then the crash comes, and when one crashes, it tends to end up being much, much harsher than the initial rush (though that is always very subjective because while one tends to crash after the rush, when the crash comes, the rush is suddenly a distant memory).
What Lewis is suggesting (and what many other Christians also suggest) is that what God provides is that sense of joy and contentment that, well, may not be as intense and as strong as say ecstasy, but is a type and form of joy that gives one strength to continue. Personally, I would suggest otherwise because Christianity is not all beer and skittles (just ask a martyr, if you could because, well, martyrs end up being, well, dead), but what Christianity gives you (that, well, ecstasy doesn't) is not just a sense of hope, but a hope that all of this bad stuff will simply not last forever.