The correspondence starts with a 1943 letter from Clarke to Lewis. Clarke was at the time a 25-year-old nobody, who had published a few sci-fi stories in fanzines. Lewis was a fairly well known Christian apologist and Oxford academic who had started dabbling in science fiction (not yet fantasy).
The occasion of the letter was the publication of Lewis's Perelandra, which had as a principal character a rather diabolical spacefaring physicist, and an undercurrent (at least as Clarke read it) suggesting that proponents of space travel were generally galactic imperialists bent on overturning the natural order of things. Clarke objected ("somewhat violently") that this is a bit of an exaggeration: "Because stories of interplanetary imperialism and destruction are the stock in trade of the hack writer, you seem to imagine that there exists a considerable body of people looking forward with over anticipation to vast wars of conquest over the surface of an expanding sphere centered upon the earth". He then goes on to defend what he sees as the much purer motives of the interplanetary societies advocating space travel that were then quite common.
Lewis wrote back with a short reply, in a very bizarrely abbreviated and emphasized style of writing that apparently is how he writes letters, that he agrees most scientists are not really like the Professor Weston of his book, but that the glorification of science and technology above all would inevitably lead in that direction.
The rest of the correspondence is somewhat intermittent. In 1946 Clarke invites Lewis to one of his lectures and is turned down, though Lewis adds, "I wish your lecture every success except a practical realization of space travel!"
In 1953, now chairman of the British Interplanetary Society, Clarke invites Lewis to a meeting of that Society, but is again turned down, though Lewis professes not to be put off by the possibility of being a rather unpopular minority if he were to come. He adds a similar benediction: "convey my good wishes to them as regards everything that but interplanetary travel" (particularly amusing as interplanetary travel is really the only purpose of the Interplanetary Society).
They do have a flurry of interesting discussions through 1953 and 1954 in lieu of ever actually meeting, and Lewis makes a number of comments on stories of Clarke's that Clarke sends him copies of. Lewis remains staunchly of the opinion that space travel brings out the worst in man and will harm the rest of the galaxy too, especially if it has life in it. Clarke tries to convince him otherwise, but is not too successful. On a side note, it's interesting to realize that 50 years ago both sides seemed to assume that widespread interplanetary travel in the forseeable future was quite likely.
The volume itself
The correspondence is interesting, but the volume it's published in is really kind of bad. There's an obvious reason this correspondence wasn't published until over 50 years later: there's less than 20 pages of it. To pad out the volume into something publishable, the publisher has included another 150 pages of filler, some of it worthwhile but most of it subpar. There is a long and rambling introduction about the process of editing and publishing this volume, which apparently went through some false starts: all well and good but I really don't care. There are 10-page biographies of each of Clarke and Lewis, which is okay I guess but I can get better biographies elsewhere, probably even on Wikipedia. Of somewhat more note, there's a two-page preface by Arthur C. Clarke, which gives a few 50-years-hence comments on the correspondence. Finally, there are reprints of a bunch of short stories from both authors to pad the volume out.
More problematic than the filler though is that the editing job is horrible. Clarke's letters are for the most part fine, but Lewis appears to have written in a strangely nonstandard sort of English filled with shorthand and abbreviations, and the editors have done a very bad job dealing with that and informing the reader which bits are original versus typographical errors on the part of the editor (the latter not only a theoretical possibility, as there are several in the introduction). In particular, a handful of "(sic)" annotations are infuriatingly thrown in after things that aren't particularly surprising, while pages of strange spellings and what might or might not be typos are unremarked upon. There are fascimiles of a few of the handwritten letters, but printed so small that they serve no use but to take up space. I suppose this is what you get when you let a company named "ibooks" print books instead of running Web 2.0 sites.
That said, the book is still worth picking up. The publisher has gone out of business, the book is now available from lots of places as a remainder for under $4, and it documents an interesting tidbit of history not published elsewhere, giving in the process a bit of a window into the interplanetary societies and such of that era.
ISBN 0-7434-7518-6, published 2003