Just google them. The first google result for "harry potter and the philosopher's stone word count": 76,944 words
Is that all? Wow, it felt like more. Hmmmm... my novel is fast approaching 50,000 words, and I've not even gotten to the 'Big Plot Development' yet. This makes me wonder...
The first draft of my novel was 200,000 words. I expect to cut it way down in redrafting... and have made an effort to do so as I've begun the process. I have read that 110,000 words is considered the "maximum size" for an author's first book of having any hope of even getting considered for publication. Don't worry if it's your first draft. Just write. You'll be surprised at how much fat you can trim off later.
There is no common word count. It depends on the genre, demographic, and what the editors are willing to do. If they think it's worth the cost, they'll publish something longer. If they don't, they won't.
