BOOKs is obsolete, I think..

Back in the V2 client, you could put BOOKS in your dsm.opt file and point to
the BOOKMANAGER (I think) files for the ADSM manuals so that ADSM would know
where to find them when the user clicked HELP.

I don't think it applies to current clients, you don't need it - the GUI has
WIndows-style HELP now, and the HTML versions also get installed in the
program group.