On Publishers and Agents

Wanting an unbiased critique of my manuscript, I decided to send it to several publishers and agents.  However, after some research, I found that isn't possible.  None of the big publishers and very few of the others will accept  a manuscript that isn't submitted by an agent. But wait. Agents won't look at your manuscript either.  You have to submit what they call a Query Letter.  If writing a novel isn't difficult enough, they expect you to write one paragraph describing the masterpiece you've worked on for months, maybe even years, in one scintillating paragraph that so intrigues them that they ask to read a few pages of the actual book. Not one page, but one paragraph. The second paragraph of this letter should be devoted to your other writing accomplishments which, the books tell me, should only include stuff you've had published. Talk about a catch 22. 

The letter should include how your book is different from all the other books on the market.  But what I'm trying to sell is a murder mystery.  Someone dies, clues come to light, the detectives finally solve the murder, that's the genre.  The only real differences are my own writing style, the twists and turns of the plot, and the characters I create.  Unless I add zombie killers, or turn one of the detectives into a vampire, no wait, that's been done, how different can it be?  How do they expect me to explain either the intricate plot lines or the characters on one lousy paragraph?  On the other hand, why do they want it to be that different anyway?  Mysteries are big sellers.  Why wouldn't you want to find another Agatha Christie? (Not that I would be bold enough to compare myself with her, but just saying.)

Okay, so in spite of the obstacles, I gave it a shot. Most of them simply didn't reply.  Others sent a one line email saying essentially, "Thanks but no thanks."  I didn't even get a critique of the letter. Back to square one.