Question of etiquette

An agent suggested a project to me in June. I took him up on it, consulted him once or twice in the interim, wrote the proposal and two sample chapters per his advice, and submitted them now almost four weeks ago. He acknowledged their receipt, promised to be in touch soon, but so far, he hasn't said whether he likes what I've done. We've been in touch once since I submitted the proposal, regarding an article he suggested I write, but other than that, nothing.

Were this a blind submission, I wouldn't even be watching the calendar. But because he solicited the project, I'm wondering whether it's time to prompt him, or whether that would be pushy. What's your take, and have you ever experienced anything like this? I'm going slowly crazy . . . though my family probably thinks the process has accelerated.

Yes, it's a nonfiction book proposal, but it didn't happen quite like that. I'd actually submitted a novel to him, and he remembered one of the nonfiction books I've published, which he admired, and which he thought qualified me to write the project he had in mind. We've had two long conversations about it and two or three email, interspersed over a four- or five-month period. Not that the circumstances change anything; in fact, you'd think he'd be quicker, given the background. Well, maybe you wouldn't, but I sure do, 'cause I'm the one sitting here wondering what's going on.

But I agree, there could be many legitimate reasons he hasn't responded.