[I have avoided spoilers in this review, so anyone can read it.]
I read and enjoyed Colin Wilson's first two Spider World novels - The Tower and The Delta - when they were published in 1987 - the two volumes from Grafton books make up one novel - and I have recently finished reading them aloud as bedtime stories. The tow books make up one story arc.
(I mention this, because on Amazon there is a confusing plethora of names and volumes - if you buy the 1987 Grafton paperbacks you will get what you need. For some strange reason the novels are out of print.)
I would highly recommend these books. Reading aloud a novel, in short nightly segments, places considerable demands on a book - and any story which can survive this treatment and still seem satisfying and worthwhile - both night-by-night and overall - is a book to be reckoned with.
Spider World passed this test with flying colours.
Perhaps the best recommendation I can make about Spider World is that after something like 1000 (large) pages, the end of the novel, the conclusion of the plot, is very satisfying - both in terms of bringing together the threads, and also spiritually; and how seldom can that be said of a book?
Spider World depicts a society in which humans are slaves (and food) to highly evolved and intelligent giant spiders, or else the humans are hiding in remote places as small precarious groups of marginal hunter gatherers. It is not just the spiders that are gigantic, but many other bugs of various types: a dangerous place!
The basic situation makes for plenty of excitement and adventure, but the main focus of these novels is psychological - they are about the powers of the mind (actual and potential) such as will, concentration, intelligence, telepathy and animistic sensitivity to life.
The whole thing is written from the perspective of the hero Niall, a young man with distinctive psychological (or 'psychic') gifts. As the plot unfolds, he (and we) discover how humans got into this situation; and discover also the powers of the mind which enabled spiders to become the dominant (or co-dominant) species.
Like all of Colin Wilson's work, the underlying theme is human consciousness, and its expansion and strengthening - but in this instance the theme of consciousness is deepened by a convincing and rather beautiful religious dimension.
The first two-volume Spider World (i.e. The Tower and the Delta) was followed by another two stories set in the same world, which I will not discuss here.
But clearly the Tower/ Delta is a very considerable creative achievement in that rarely-successful genre The Philosophical Novel - and deserves to be much more widely read (and to be reprinted!).
In the meantime, you would be wise to snap-up the cheaper secondhand copies, while they are still available.