ncbi...eutils/esearch.fcgi: How to search now in the snp database? According to the 2017(!) textbook, it worked at that time, for instance, 

https://eutils.ncbi.nlm.nih.gov/entrez/eutils/esearch.fcgi?db=snp&amp;term=autism

At this time, this does not work and for each conceivable term it will find 0 records. 

What is the right way to search in snp, valid in December 2018?
eUtilities for dbSNP is in the process of being retired. See this post from NCBI. You may want to check out the new API.
From the NCBI Insights blog post:

Entrez search is available only for human. We will retire all Eutils report formats (RS docsum XML and ASN.1, FASTA, and FLAT text) later this year. Only eSummary XML report will be supported.
Batch Query Service for all organisms will be retired October 2018. Users of human dbSNP data should transition to the new API.
We will place non-human FTP data in the archive directory. Please see the phase-out plan announced last year.