Hi Karen & congratts on your deciding to build an Ob's
Attached is a pic of the bigginings of my Obs, nothing Flash but is strong and serves the purpose very well. as can see I had decided to go with a flat style roof but with a small pitch to deal with rain water, not to complicated to build, and can note the corigations run down hill for rain flow.
Also of note, is the High end of the Obs is facing South, pitched lower than the South Cellest Pole so I dont miss any of the Great target in the polar region, and accordingly the lower side facing North which allows viewing range to catch the targets there, lower to the horizon !
I have built a two piece roof for two reasons, A) Lighter to handle ! B) I can have one side open and other side closed when viewing East or Visa-versa. Infact, i seldom have either fully open as I try to have open just enough to view/photo through, thou need to adjust during longer image sessions, this helps reduce due forming in the obs during the night since this is my Obs away from home, Dark Sky Location, I have a camp bed in there which is against the western wall, there it seldom gets wet from due, not such a pleasure during cold winter weekends ect , I mention this as referance/idea with your bookshelving, just some thoughts for this !
In addition with moisture condensing on things, I suggest you have a reasonable material for your book shleving, bare partical or bare MDF board wont stand up to heavy moisture, so I good coat of Paint would do the trick in this case ! The good thing is, that due normally only reaches areas directly under open air, so if you have a top shelf cover then everything under it should be fine ,, maybe a curtain or similar infront of the shelving, just to be on the safe side : )
Hope this is of help and there are many ways to addapting your own obs to suit your own needs, & wish you all the best with it all ,,
