You can register to become a researcher at reception, but you'll need two forms of I.D. Its open weekdays only and if you have any botanical interest, its well worth a trip. Bear in mind its closed mid August for annual housekeeping, but any other time so long as its a weekday is fine.
You are even allowed to take photos (no flash) of the materials for your own use, (though I didn't) if you are using it for any commercial reason (a book, a talk, a website including no mark blogs like this) then you may have to pay a fee. The Library itself will issue you with a Hi res photo for your use taken by them. (As it was explained to us, if you are going to be promoting the library, then we want the best photos for Public Image reasons.)
OK main info over, what did I actually see on my trip. If you're a long term reader of this blog you'll know I like to talk cactus now and again. So this was a trip out arranged to talk about all things cactus, with a trip down to see some seriously old books and some botanical art too. After a brief talk in the upstairs library and an explanation on how they work (fun fact books are separated by genera and not language so if you want German works on cacti you'll need to look in the cactus subsection) we headed downstairs for our main talk.
A tiny room with a few PC's, bookshelves and a set of tables with books seated on cushions that reminded me of people loafing on beanbags. This was to stop them opening too far and protect them from wear, a few were really fragile including a work on observations of a "Hyiucca" (Yucca) complete with uses and pictures.
The first book was a dutch herbal from the 1500's detailing the use of Aloe's in medicine. There were a few other books with much more up to date plates from the 1600 and 1700's but the next one that really stood out was a massive red tome that looked like Lord Zetta from Makai Kingdom. This had some really gorgeous artwork of "Aloe" as well as being really detailed, there were plates that looked much more modernist to my eyes, especially one yellow Aloe which could easily have been a poster from the 1930's.
The last book was only tangentially related to Cacti, being a work on citrus fruit, lemons and the like, but with the odd inclusion of a large drawing of Selenicereus Spinulosus with a map of Nuremberg and its attendant villages in the background. We ended up looking at some botanical art, which included plates from a failed book project from the 1600's (shades of Kickstarter there) and how they typeset pages from the old Vera Higgins books (hint is largely a collage of single drawings put onto white paper). The last thing was an impressive picture of Astrophytum Ornatum, the lady told us it took three attempts to make this as the artist wasn't happy with it. After that and looking around the library for a bit decided to go home, all in all a great day out.