After Harry.

Is it just me, or is this list of recommendations somewhat uninspired?

I think we can probably do better than that.  For one thing, the HP fanbase is so broad that it depends on who we're recommending books to -- and for another, people like the books for different reasons.

So, as a start:  I most definitely agree about Diana Wynne Jones -- the Chrestomanci stories and Howl's Moving Castle for the younger HP fans, of course, Dark Lord for those who have read enough fantasy to recognize the affectionate jabs at the genre and for those who are looking for a large cast of likable characters, The Merlin Conspiracy for those who enjoyed the politics of HP, Fire and Hemlock for older teens (and adults -- heck, it took me a few reads before I got it) who'd appreciate a good Tam Lin story.

...

Oh, sorry.  Got distracted -- I just checked DWJ's website (I was blanking on the title of The Merlin Conspiracy) and noticed this blurb:

HOWL'S COMING BACK – Fans of Howl will be delighted to know that Diana is working on a new book which will include a guest appearance by the popular magician.

Ooooo!

Sorry, busy dancing around about that -- you'll have to come up with more post-Harry suggestions.