I am trying to find out about the Minhagim/customs of the prewar Amsterdam Jewish community. Would anyone have any recommendations of which sefarim/books discuss this?
In addition to the excellent answer of @Dov I would add a link to minhag-resources on the website of the Dutch Jewish Community.
There is a mix of modern and pre-war; Most of the info is curated with the express purpose of maintaining the minhagim of prewar and just post-war communities. Much of the info pertains to Amsterdam such as the Amsterdam-specific stops for Acharon in Torah-readings as opposed to e.g. the Acharon stops in the Hague (p19)
Of importance are the Regulations of the Ceremonial Order from 1901 which gives an insight into the rules followed in Amsterdam shuls before the War. For example rules for who could say Kaddish (Chapter 3). The document is in Dutch and I have not found an English translation of it.
Old Amsterdam traditions concerning Torah-reading are summarised on the website itself (mostly unsourced): https://www.nik.nl/chazzanoet/Laienen/Laienen.htm . The page also includes links to the typical Amsterdam/Dutch trope for laiening for shabbat, purim, etc.
There is also some notable chazzanut. To highlight some pre-War Amsterdam specific parts:
- Pesach melodies (sheet music) from the 1939 Staal Haggadah
- Melodies sung in the house of Eljakim Asscher (1879-1944). e.g., Shir Hama'alot for Pesach
- Jewish Hymns (e.g., page 4-7) by the conductor of the choir at the Great Synagogue in Amsterdam: Samuel Henri Englander (1896-1943).
All of the above is fairly Ashkenaz-specific. The Portuguese-Amsterdam traditions are not so specially curated by the NIK. There is however a good online resource which unfortunately is not updated AFAIK, http://www.chazzanut.com/ . The focus here is on chazzanut more than on minhagim in general. But the website gives an excellent overview of the pre-war musical traditions in both the Portuguese and Ashkenazi communities such as Amsterdam, such as Kaddish for a wedding recited by pre-War Chief Cantor Bentsion Moskovits.
Of special note are the rather uniquely Dutch/Amsterdam melodies for the Priestly Blessings (Birkat Cohanim) and their description by Aron Wolff-Berlijn (1864). The melodies for the Priestly Blessings differ depending on the Festival or High Holy Days, and between shacharit, mussaf and 'matenad jad' (the days when the end of Reeh (concluding with the verse איש כמתנת ידו) is read from the Torah, namely 8th day Pesach, 2nd day Shavuot, and 1st day Shmini Atzeret. in which melodies follow the Jom Kippur scales).