If you have the books for it, I'd do it. But I wouldn't if the bookshelves are primarily intended as decorative space. Also, I think it would look less busy if you have some book groups, like in the inspiration picture on the shelves above the ladder rail, that have matching spines. Don't get me wrong, I'm not suggesting the (in)famous books-by-the-yard decorative fraud. And I'm not among the anti-"clutter", get-rid-of-so-many-books crowd, either. I live with more 10,000 of them and they are everywhere in my house on shelves that span from skirting board to cornice molding. But your inspiration photo appears to have one densely booked-up wall while adjacent ones are normal. That mitigates the overall effect in an attractive, not overwhelming way, at least for ordinary, less book-obssessed households than mine. Two other things (besides the dusting issue): a) the thought of books in a conservatory makes me a little nervous because of the potentially damaging moisture issues, and b) windows that large will expose the books to a lot of very damaging UV light. Not a good thing for books with any intrinsic value. You could cover each book with a library-quality mylar jacket, but that would only delay, not eliminate, long-term UV damage to the covers and DJs. My most valuable books are kept in a room with relatively low external light and I make a point of not leaving the lights on in that room except when I am in there using it. But if you are, like me, intent on living with your books on a daily basis then have them where ever they can fit. And more shelves offer the possibility of more book purchases, so there's nothing discouraging about that! L

There are a lot of "it depends" answers given how open-ended your question is, and only you can set those parameters. It depends on what kind of tools you want to use, and how much you want to use each one. I could figure out a way to build a pretty solid bookshelf using only a circular saw and a drill because I hate using a table saw. But if, like many here, your table saw is like your third hand, then your options expand. In addition, do you want to be messing with glue and edging on plywood? Solid wood is far simpler. It depends on what kind of wood you like. Personally I have very strong taste in wood and would pick based on what I like of what's available - wander the aisles at the lumberyard. And some woods are stronger than others, so the decision about what wood to use is connected to your preferred construction method. Warning: some are also heavier! You are definitely looking at a substantial span there, and I too would worry about sag whether you use plywood or solid. The various bookshelves I have that aren't sagging (I didn't build them - and they're no where near your span) either have the shelves nailed to the backing (from behind - this is surprisingly effective even when the backing is only quarter-inch ply - or are at least 3/4 inch thick solid wood. If I have my physics right, foot-wide boards will be stiffer than narrower ones too. But by the way, I find narrower bookshelves far more useful; very few books need a foot of depth. But your dimensions are a bit questionable in more ways than one. This is going to be a honking big piece of furniture that I wouldn't be able to navigate into some of the rooms in my house, much less set up in them. It would solve both your sag issue and their mobility to make two smaller units instead of one big one. Even if it's perfect for you at the proposed size, moving it or selling it will be torture - think transportation. Make two narrower units and they'll fit in any hatchback. The piece you're proposing will only fit in a truck. But whatever size you make, if you stick with that height, make sure you devise a way of fastening your unit(s) to the wall. KarinL

Boxerpups, I needed those images. Thanks so much! Isn't it amazing how a simple image can clarify so many things? Am reminded about the architect Sarah Susanka's comment that bookshelves are like wonderful wallpaper. I hope that my cookbook collection and the other items I need to store on shelves will function in that way. Was on a road trip to a wedding recently and had lots of time to make sketches. I have a better idea of my bookcase options now, but hadn't been able to picture the moldings and such. These images are very helpful. The red-painted shelf units with the curved trim are so intriguing. Wonder how they suspend those long shelves? Or did they make a vow to only store lightweight stuff? The images of various same-width multiple shelf units are extremely helpful; You're a painted cabinetry gal, aren't you? I am trying to imagine them in oak instead of paint. These regular soldier-like niches are likely what we'll end up doing. The over-the-door shelf is something I had considered but DH vetoed. Now that he's sat with me looking at your images, it's back in consideration again. I am supposedly working on the denoument of this project's planning but am still dithering about cabinet glass for my kitchen so I went to a local glass company to talk. They said they make lots of glass doors for labs, businesses, etc. I think that they would help me with sliding glass doors for bookshelf if I want them. They are in the custom glass etching business so they can even temper and etch decorative (textured) glass, which would allow me to get a strong, textured, opaque effect for lower shelves that may accumulate junky stuff. It would be expensive, but extremely distinctive. (This added to my dithering and got me off track, again.) [Confession time: Problem is further compounded by seeing an antique piece that would work in that space also. Unfortunately, when he was working on wallboard phase, DH refused to wallboard the back side of the bookcase space when it would have been easiest to do it, claiming that it would be redundant work. So there are literally a number of holes into the inside of the wall on the back of the bookcase niche to contend with if I win the piece at auction. Am in another quandry. Best solution: stay out of auctions and antique shops and estate sales.] ___ Leel: would love to learn more about the steel shelves you have used. Sources?

Thanks. I'll be in the space tomorrow and post a picture. To the extent it helps, I just drew a quick layout - not exactly to scale but gives the basic idea. So the question would be: should the built-in bookshelves extend all the way to the corner or would that look off balance. Also, if the bookshelves do extend to the corner, how far along on the other side should we go? We didn't want to quite go to the entrance of the livingroom because then we would be narrowing the entranceway, but maybe we have to under to balance things out. Thanks so much for any thoughts!