Off the Bookshelf: THE DIMENSIONEERS, by Doris Piserchia

I discovered this book many, many years ago, at a used bookstore, and over the years wished I never turned it in during one of my moves, in an effort to cut down on the number of boxes and bags I had to haul ...

Ah, the joys of finding some classic spec fic released in ebook!

Our heroine has no name -- no one addresses her by name, and it's told in first person, so she's just "I" and "me." Reviews refer to her simply as "the orphan." 

Very little explanation of her world is given, because she doesn't need explanation. This is her normal world. She's very intelligent, but pretends to be illiterate, lazy, and crude -- and she's able to link minds with a mutated lion-creature (called a gamber) named Wyala. Together they slip through the dimensions, simply referred to as D. Whenever she can get away from the orphanage. She's late for dinner an awful lot. And they adventure all over 100 worlds, all linked by dimensional tunnels. When the nasties at the orphanage don't get in the way.

Then she starts running into nasties in D. They're out to take over every world they touch. Think the aliens in Independence Day. And suddenly there's a rich woman who is showing interest, and the military is out to catch her (well, what do you expect, when she uses her dimension-skipping abilities to steal all sorts of weapons and ammunition from government warehouses, to help the resistance?). Life gets very complicated when the "good guys" out to save the multiple worlds aren't much nicer than the nasties.

This is a short, fun romp with some serious, frightening moments. Worth holding onto.