Stella Maris is a companion novel to The Passenger, and this was published a couple of months after that book. I read them in the order they were published, but I do think that it may be better to read them the other way round. This book is entirely a dialogue, between Alicia, genius mathematician and sister of Bobby, the main character in The Passenger, and her psychiatrist. It's a fiercely intelligent conversation about mathematics, physics, religion, the meaning of existence, madness and philosophy. It's very readable, if challenging to absorb, and profoundly questioning.