How to value "inventory" of salvaged junk for tax puposes ???

Hoping somebody can assist here..

I've run a small property maintenance business for many years .. always considered a "service" business with no inventory. Over the years I've salvaged books & misc. small objects rather than take them to the local dump .. eventually filling a garage with such "junk".

Recently I've begun to cull through and discard most of it .. excepting some books & paper goods I've listed for sale on Amazon. Last year sale of these books etc. was a few hundred dollars... with another several hundred books listed but unsold.

Do I now have "inventory" that must be accounted for on my Schedule C ?? Do I need to declare & value such items or can I simply sell them off and declare the proceeds as "miscellaneous business income incidental to my other revenues. If my accounting method is "cash" and my cost basis for the stuff is zero .. is the value of this "inventory" zero from beginning to end. any advice appreciated

Dazed N. Confused