Ascension a novel

Your basic, man goes on a journey and comes back crazy novel. Told, of course, in epistolary form. Harold, our returned man, is a physicist polymath, thought dead for over 10 years is discovered in a hospital by his brother along with a packet of unsent letters. The letters tell the story of a doomed, and ultimately covered-up, expedition on a mysterious mountain where neither time nor geometry can be taken for granted. In parallel, Harold’s tragic life prior to the expedition is revealed and religion is discussed. I finished this 350ish page book in about two days so I would say it is a bit of a page turner.