Congratulations on building your house! And congratulations on choosing a metal roof! It's way more economical in the long run, due to upkeep savings, and saving on cooling, if you live in an area that gets hot enough to worry about AC anyway. With a standard tar paper roof you gotta replace the shingles every few years...or if they're blown off...and it feels like it tends to leak a lot. Maybe there's some other type of never roofing technique that's a bit better, but metal roofs really seem like the best choice of the most common options.
The reading loft also sounds awesome!