I started rereading these a few weeks ago. The first in the series, Fer-de-Lance, was published 80 years ago and yet the language is still ...um... current.
The Doorbell Rang about the FBI may be of current interest.
In any case, a good library should have them. Obviously, I think they're worth reading, and I'd like to find out if younger readers agree.
If you're in a library and at loose ends, pick one up, and let me know what you think. Thanks.