tax question: royalties

Those of you who have textbooks or academic books for which you receive royalty checks, where do you list those royalties on your tax return? I have only been receiving these since 2005, but for 2005 and 2006 I listed mine in line 17 on the 1040, which is rents and royalties. That line mostly looks like a real estate issue, though, and it mentions oil and minerals and the like. I always just figured it all fell under the loose term of property. I just now read the instructions for that line, though, and it says that authors should put royalties under business income, and that's where turbotax directed me to put them this year. If I understand that correctly, that means you have to claim something like a side business. And so now that we have filed that way in 2007, the IRS has written to inquire about my 2006 royalties. Really, it's quite sad that taxes are so complicated.