Timothy Zahn wrote a good speculative book about potential life on Jupiter. I read this 6 or 7 years ago:
And I'm currently reading this one:
While Zahn has a master's degree in physics and never worked as a scientist, Forward was a real scientist that later wrote science fiction. Forward's novel, Saturn Rukh, is aptly known as hard science fiction, which means the science is as real as possible. Life on Saturn is simply a speculation, which makes the novel one of speculative fiction, which most people simply call science fiction.
Thinking about Jupiter and Saturn isn't terribly difficult, since they are somewhat familiar planets. In some sense they can be considered small inactive stars, since their cores are not fusing hydrogen into heavier elements.
For serious imagination taxation, very little can top the books below:
Have you ever wondered about potential life on a neutron star? Do you even know what a neutron star is? There's no better way to learn about neutron stars. Although I had already known a bit about neutron stars beforehand (that's why I immediately purchased and read those books after becoming aware of them), I had never myself ever considered life on one.