I'm worrying somewhat about the quadrology I am currently revising. Do I query only the first part? (They're not very standalone, they're one long book split into four.) Do I query the first part and mention the others? Do I treat the first one in detail and say 'in parts two three and four, Rhailed and his friends get kidnapped, destroy a famous landmark, uncover the enemy's evil plans and foil every stage of them before making major changes to the governance of their kingdom and making tentative peace overtures?' Do I go into detail for the whole thing?
this is non fiction right?
You query the whole darn thing. However, you don't just recite the plot. What makes this compelling? What will draw the reader in? Why on earth do I want the good guys to win? (Miss Snark is bored with the triumph of good over evil.)
Then you break the news about length. SFF skews long so seven gazillion words is not a deal breaker in this genre (there are posts about that earlier on the blog). Tell me that this saga unfolds over four books. At this point its not important to know which book covers what. What's important is the concept and the execution. You tell us the concept, and how well you write those pages and your cover letter tells me about the execution.
Detail is the devil in query letters. You can't go into much, but broad generalizations are boring. You have to find one or two compelling details that really entice a reader. Try not to panic though. Even if your query letter truly sux (9 out of 10 do), if your pages are good, you're still in the game.
And why are there no SFF characters named Susan? or Fred? or Barney? Do they all have to have unpronounceable names? F'lar, Lessa, schmessa.