
Originally Posted by
Fame
Let me try to redo this, and (A) is adverbial:
These books(s) are(v) the best novels I could find(SC).
I(S) gathered(V) the leaves(DO) into a pile(A).
James Wong(S) is(V) the fireman(O) who fought the blaze(OC).
The farmer(S) herded(V) the goat(DO) into the pen(A).
I think it is better now.

[1] These books (S) are (V) the best novels I could find(SC). 
Note, a better way to form that sentence would be to omit books.
Ex: These are the best novels (that) I could find.
The relative clause (that) I could find functions adjectivally. It modifies the noun novels.
[2] I (S) gathered (V) the leaves (DO) into a pile (A). 
[3] James Wong (S) is (V) the fireman (O) who fought the blaze (OC).
Note, sentences [1] and [3] share a similar copular pattern, yet in [3]
who fought the blaze is an (OC). Why is that?
Note also, object complements are used after certain verbs only.
An object complement is often found with verbs of perceptions, thinking, or verbs that denote a change. - Many people consider Churchill the greatest British statesman.
- We decided to paint our house red!
- They named their child Thomas.
Object Complement - ICALwiki A way to CHECK if the element following the object is an OBJECT COMPLEMENT is to form a separate sentence using the object and the supposed complement with the verb "to be". If this is possible, then the supposed complement is in fact the OBJECT COMPLEMENT.
See examples here
Syntax Lunacy: OBJECT COMPLEMENT [4] The farmer (S) herded (V) the goat (DO) into the pen (A).