This evening my SO and I sat down at our usual Chinese restaurant and I soon announced that I was beginning to read chapter one of volume 2 of Northanger Abbey. I was soon asked why they were printed in multiple volumes, especially since my current copy is quite compact. Even acknowledging the high possibility that the type in my copy is notably smaller than that of the original publication, I had no answer to give. My searches here have come up empty (although I may have chosen the wrong words for the search).

Can anyone help me explain why Jane Austen's novels (and other novels of her day) were published in multiple volumes? Did it have to do with limits of printing and binding techniques and practices? Was it to keep the books small for easy handling in the sitting room in the evening after dinner? Was it merely a writer's convention without any physical need to explain it? Or was it something else entirely?

Thanks.