In Earth’s future, tunnels are found on Venus that contain alien artifacts left behind hundreds of thousands of years ago. Later an asteroid is found that is riddled with tunnels and studded with nearly a thousand small ships, most of which are in working order. The ships will travel faster than light to a preset destination, and return automatically, but no one knows where the destination will be, and a significant percentage of ships either never return, or return with the crew dead. Of those that do return, many return with alien technology or data on valuable locations, making the crew very wealthy. This has set off a sort of gold rush, with people spending everything they have to get to the “Gateway" asteroid and gamble their lives on the chance to get rich. The story is told through the eyes of one such man, who has gotten to Gateway, but then is too scared to take a mission. This is an amazing book. I read it originally in the 80s (it was written in the 70s), and I believe this was my first reread since then. I can’t recommend it strongly enough.

Edit: Sorry for the double post - I was having issues with my internet connection and was getting posting errors, but one of them must have worked. I deleted the other one.