How much is too much. I'm sure everyone who writes and does research finds so many things that are interesting. Some writers try to put them all in a book. Then the story turns from fiction to a "let me tell you all about -----" That's what they've recently researched. I've been guilty of this, especially when I'm working in an historical period or with medicine, present and fantasy. Unfortunately just because some bit on information interests you, doesn't mean the reader will find this interesting. I once, while writing a medical inspired romance detailed an entire surgery, pages of what was fascinating to me, but when a friend read the scene she shook her head. "She didn't want to be a surgeon, all she wanted was the flavor of the operating room and the reaction of the characters in a short scene. My friend was correct so I condensed what I'd found so fascinating.
Here are some points to remember when putting facts into a story.
1. A little bit goes a long way,- Instesperse the facts with the meat of the story.
2.No long passages of fact. Enough to interest your reader but not to put them to sleep.
3. Don't let a character become a lecturer or a teacher unless they are one. Then tone down their teaching moments.
4. Make sure the information comes at the right time. Giving the facts to show a historical period too far into the book may leave the reader scratching their heads.
5. If you've chosen a career for your characters that you know nothing about, find someone who practices that field. They can give you little hints that make your character seem genuine.
6. Keep your time period in mind. Don't use words that pull the character and the reader out of the era of place you've chosen.