I've been working on a novel since August last year and I'm about half way through. But I came up with an idea for another novel and I've started writing that too! Has anyone else got multiple projects on the go? I don't think it's a bad thing. But I do feel like I'm cheating on my first novel :-)
I'm not a good multi-tasker. I like to finish one off before starting another one but I have usually have the ploline and characters all ready and waiting for me when it is time to start the second one so I know that I don't forget what I was so excited about in the first place.
Before my first novel was finsished I pretty much had the same problem. I couldn't consolidate an idea without becoming drawn to another one. My tilogy has been the first idea I have ever truly fallen in love with. I am currently writing the second draft of my second novel and the first draft of the third and final part of the trilogy at the same time. So long as you don't get confused and start writing the end of one book in the middle of another I can't see any issues :)
The same thing has happened to me. I was in the throes of drafting a novel and then I came across a travelogue book which had nearly the same title as my novel. Thus, It inspired me to write my own travelogue which is now complete. My answer is that no I don't think it's a bad idea as it's given me more inspiration for my novel. Hope this helps