Strange Attractors by Jeffrey A. Carver
This is the second book in Carver's "Chaos Chronicles" series. The main character, John Bandicut, finds himself in Shipworld, a vast collection of habitats or small worlds. Each habitat is link to others by portals which seem to behave like teleporters. It is not entirely clear what the entire size, shape or arrangement of Shipworld is, or even how far away the different habitats are.
Bandicut is guided to some degree by Shipworld on a task it wants him to carry out. He is accompanied by a couple of being he finds there. He also gets some help from a progressively re-generating version of Charlie, an alien friend (which lives in Bandicut's head) who died in the previous book in the series.
There is interesting scenery and life forms along the way on his journey. We also meet a few kinds of aliens and some vast technology.
It turns out that the major crisis in the book involves Shipworld's computer systems being threatened (and some areas taken over by) something like a malicious software entity. Although it's existence and activities do not end up being attributed to the equivalent of someone releasing a computer virus with the intent to do harm, it is a serious danger that needs to be dealt with.
Some aspects of the book are murky or seem to lack logic. Some of the aliens are implausible, etc. However, the story could be an interesting romp for some readers, perhaps more so for younger readers.