I assume the new Harry Potter book, and the last one, will - as usual - have a big magical pitched battle near the end. These battles are what I like least about the books, because every bit of them seems arbtrary: who hits, who misses, whose spells and attacks have the greater power. In general, for me, a fantasy book beguiles by creating an enjoyable sense of consistency in a made-up world. Such consistency invites what J. R. R. Tolkien called "a willing suspension of disbelief." But my willing suspension fails during these Potter wizard battles.
The trouble however is that the Potter movies have GOT to have these battles, so they better be in the books too, or else the faithful readers will complain.