Here is the link to Springer.com, where you can find > 300 OA books:
Many thanks to Frank Nielsen, who posted this link on X: https://x.com/FrnkNlsn/status/1866459105789128852
You can also find our OA book „Hyperparameter Tuning for Machine and Deep Learning“, which has more than 100 000 accesses, in this list: https://link.springer.com/book/10.1007/978-981-19-5170-1.