How large is it?
Roughly 8" tall by 6" wide. Almost 900 pages. Quite hefty and definitely not pocket-sized, I actually leave mine at home when I go to church. I have heard rumours that they will be producing a lighter version that is not so comprehensive--really this contains more than the average layperson would ever need--but checking with my sources, that project isn't off the ground yet.
It's not 8 x 6. You made me dig up a ruler and actually measure it. It's just a tad taller than 6" (~6.5') and wider than 4" (~4.25) and about 1.5" thick.
....a bit thick for a pocket, but, nonetheless comprehensive, and well worth having.
Are we still talking about the UOCC prayerbook, published in 2007?? I have one in my hand right now, and though I don't have a physical ruler, the online ruler at iRuler.net, adjusted to my screen resolution, measures the book at 7.5" tall, 5" wide, 1" thick. My previous measurement was more rough, based on an icon I have of that size.
The measurements you give remind me more of the previous edition, that was released pre-2006.