Think of all the people who will read this post. I assume we all like to read. Or take all the folks browsing in Powells right now. Even though they all like to read, I can guarantee you that there is not one book that they would all agree was great.
The same is true of agents. One agent's delight is another's snore. When you are looking for an agent, you may have to query dozens. Rejection doesn't mean that you have written a bad query letter, although it could. Esp. if no one ever asks to see a partial. But if people reject your partials or fulls, that doesn't mean it isn't a good book. (Although, again, it could). It could also mean it's just not right for them.
This is a truncated version of my publishing history, which I recently shared with someone on LJ:
1. Wrote book based probably far too closely on my experience working at a hospital. Was sure would be soon be millionaire.
2. Got dozens of rejections.
3. One agent eventually called me and spoke to me for an hour. She wanted the whole thing revised. But by that time I was busy with #4.
4. Wrote another book, told in four first-person POVs, about a woman who realizes she was raped by her father as a child. This was very cutting edge. There were no other books out there like this. Was sure would soon be millionaire.
5. Got dozens of rejections. Probably more than 50.
6. Wonderful agent offered to rep. me. (Was sure would soon be millionaire). Agent said, "It's so good, I must be the first agent you showed it to." I stammered something about "a few other agents." Her voice sharpened. "How many?" Mentally cursing myself, I mumbled something like, "Five or six?" To this day, she does not know the truth.
7. Agent sent out book to every single publisher in the world.
8. Variation of #s 2 & 5. Rejection letters were glowing: "lyrical," "deeply moving," "magical." Yet after two paragraphs of praise, the third paragraph always began, "Despite this," "And yet," or "But I'm afraid..."
9. Wrote a third book, a meticulously researched book about Orphan Train riders.
10. Agent sent out book to every single publisher in the world.
11. Variation of #s 2& 5, except these were bored publishers. Writing perfunctory letters. "Thanks, but not right for us," that kind of thing.
12. Wrote Circles of Confusion while coping with first baby. Learned it was possible, if one was desperate enough, to nurse AND write.
13. Book sold in three days. However, was not millionaire.
14. This is something like a six or seven year overnight success story.
I don't know if you can learn a lesson from this. Not every book is good enough to be published, or to find an agent. But perseverance does pay off. But often not when you want it to.
As my mom says, "There's never a door that closes but a window opens." And then she adds, "But the hallways are a real bitch."