Besides "Gathering of Animals," mentioned by Octopie, there are two good history books each called "The Ark in the Park" - one by Wilfrid Blunt (London Zoo - 19th Century only) and one by Mark Rosenthal (Lincoln Park Zoo). Vicki Croke's "The Modern Ark" (we sure do love our Noah analogies, don't we?) has a very good basic overview of zoo history. There's also Hagenbeck's classic "Of Beasts and Men"
Auckland Zoo Auckland Zoo opened in 1922 and has a fascinating history. I’d throughly recommend reading through this thread: Auckland Zoo History [Auckland Zoo]. The most recent post contains photos of historical features that still exist to this day - old elephant house and pool etc. This map from 1926 illustrates what an impressive collection they built up in just four years: Photo credit: @zooboy28
Here are some historically important zoos regarding to zoos themselves. The Hagenbeck Tierpark in Hamburg is important because it is the first zoo to show animals in exhibits without bars. The Vienna Zoo since it is the oldest zoos still running to this day. The Belle Isle Aquarium in Michigan for being the oldest public aquarium in the world.
It opened to fellows of ZSl in 1828. Charles Darwin was a fellow. INn 1850 a Hippopotamus arrived there and it was the first Hippo seen in Europe since Roman Times. In 1853 they opened the first public Aquarium. London Zoo has several Graded structures which means they can't be destroyed such as the Giraffe House which has been there since 1836. It closed for just 10 days during WW2.
A few additional snippets that might be of interest: Indeed Charles Darwin was a Fellow of the Zoological Society; Darwin was particularly interested in London Zoo's orang-utan "Jenny", and he visited the zoo several times especially to see her. London Zoo's first hippopotamus, named "Obaysch", arrived on 25th May 1850 (nine days after the zoo acquired its first thylacines). "Obaysch" lived at the zoo for nearly twenty-eight years, dying on 11th March 1878; he was the father of the famous hippo "Guy Fawkes", born at London Zoo on 5th November 1872.
I would recommend a different book as a starting point; like the Kisling book it was very expensive but you can get hold of it on Ebay or Amazon more cheaply now; https://www.amazon.co.uk/Zoo-History-Zoological-Gardens-West/dp/186189208X and also for London; https://www.amazon.co.uk/London-Zoo...n+zoo+in+old+photographs,stripbooks,59&sr=1-1. I think you would also find old guide books interesting and you can get them quite cheaply on Ebay.