Here are a few possiblities you might consider.
Walnut is wasteful. You need to allow anything up to 50%- 80% waste with this stuff depending on how you estimate your rough sawn stock needs-- lots of knots, sappy stuff and other faults to work around and generally only available in narrower widths. It does fume to an attractive colour, but why bother when you can do a safer, more controllable job with dyes and stains?
Chestnut, which is brown anyway could be followed up with a suitable oil based or light fast spirit based dye, and perhaps additional pigment staining to emphasise the open pores. It's easier to work than white (european) oak, but availability might be a problem. You'd need to check with your supplier.
You could use European oak or imported American white oak and dye and/or pigment stain this too. This is safer than fuming, but if you insist on fuming then you could rent an enclosed trailer and shove all your parts and your .880 ammonia in this for a day or two whilst the fuming occurs. This saves building a fuming chamber, and once the doors are open the residual ammonia fumes leave within half an hour or so. Exposed liquid ammonia very quickly becomes gaseous at room temperatures.
Fuming incidentally is difficult to control regards final colour and colour matching from plank to plank-- this is true of all chemical reaction type colouring of wood.
A third easy option if you want a fine pored or close grained look is to use poplar-- often sold as tulipwood here in the UK. It's fairly soft, easy to work, very little waste-- only about 10%, off white in colour with some green/red mineral staining. The mineral staining turns brown rapidly-- within a year usually. It dyes easily enough and if you go for the dark dye and tinted polish look you can near enough obliterate the original wood colour.
I think of poplar as mostly a secondary wood for hidden constructional parts or as a paint grade primary wood. It's not particularly attractive polished clear in my experience, hence heavy dying and tinted polish to pretty much obliterate the original characteristics.
You could use european beech too, either white or steamed, and this would probably give a more attractive end result. This stuff too is not very wasteful and it's cheap. It's harder to work than poplar, heavier and stiffer, so you'd need more time to make your library than you'd need with poplar. Beech is the classic european wood that has been used to mimic just about every exotic or expensive wood for centuries, so you should be able to get the colour you want easily enough with dye and polish. Slainte.
