I got my copies of HOP and a Haskell book yesterday. I haven't had a chance to dive into them yet. I was hoping to get them during or before the long weekend so I would have some entertainment, but it was not to be.
The Haskell book was pretty expensive, but I haven't found any of the online materials very satisfactory. I learned functional programming way back when, so I don't need all the introductory stuff, which is what the online tutorials concentrate on. I picked this book from scanning online -- I thought it looked the most useful for my purposes. I'll see if I was right.
As for HOP, I didn't expect it to be so thick! From a brief scan, I can only tell it's nicely typeset. I hope to have a chance to do some in-depth reading today.
In the meantime, work beckons....