This is the sequel to Tinker. Reading this one first is not recommended; the situation is too complicated.
Ugly Elvish politics, prophetic dreams, dragons, and Tinker comes into her own in a way that really sticks it in the other elf factions' eye. Some bad guys are redeemed, while others are confirmed as being terrible menaces by nature. A whole lot of stuff flies around and blows up, in fairly entertaining ways, but the world doesn't work quite as well as it might. 7 out of 10.
**** MINI PLOT SUMMARY -- SPOILERS ****
The stargate that the Oni built using the plans they stole from Tinker's father didn't really work. The ships that had been sent before hadn't really gone to the other planet; they were held in some kind of timeless limbo until Tinker broke the gate in the last book. Then they all came out, in Earth orbit, in the same place, and smashed each other. The doomed crew's plight comes through in Tinker's dreams as scenes from The Wizard of Oz (which Tinker doesn't recognize because she never saw it). The place where Tinker's gate was is a pool of interdimensional chaos. While Tinker is examining it, a dragon comes through it, and would have killed her and her sekasha, but Riki calls it off. They eventually learn that this dragon is intelligent and a decent sort as long as he has magic.
Wolf knows there's an Oni army on the other side of the pool of chaos. The chaos isn't fading like it should. So he calls in other elf clans, just to be sure, and the vindictive SOBs are more interested in scoring political points than in dealing with the problem. Then Tinker gets teleported to the bridge of the falling ship, where she is able to figure out the message from Impatience (the good dragon) and figure out how to bring the ship to Pittsburgh. The leader of all the Tengu is aboard the ship and pledges fealty to Tinker. It turns out that there are tens of thousands of Tengu on Elfhome; they'd been sneaking in to avoid the Oni. (The Oni made the Tengu from humans who went through the gate from Earth to Onihida; they have no Oni blood.) With Tengu help, the good guys recapture the dreadnought that the Oni had stolen and use it to kill the evil dragon. Tinker figures out how to build a controlled gateway back to Earth.