Having looked at different commentaries on Ecclesiastes in the past, I will provide a list of the ones I feel to be the most useful. To help me find reliable commentaries on Ecclesiastes I checked out “Charles Spurgeon’s recommendations. He had recommended the following commentaries which I would also recommend:
Charles Bridges in the introduction to his commentary on Ecclesiastes had recommended this book which I have not looked at thus far:
I did quickly look at Christopher Wordsworth’s annotations and what I saw was very encouraging:
Christopher Wordsworth, “The Holy Bible, in the Authorized Version; With Notes and Introductions by Christopher Wordsworth, D.D., Bishop of Lincoln – Volume 4, Part III : Proverbs, Ecclesiastes and Song of Solomon”
Each one of those commentaries can be downloaded for free. In my opinion the best of those commentaries is the one written by the American Presbyterian pastor Loyal Young.
A pastor has recommended to me “The Pundit’s Folly” by Sinclair Ferguson (available through Amazon.ca). I haven’t ordered it yet.
I cannot quite recommend the commentaries written by Moses Stuart and E. W. Hengstenberg since they each adopted the erroneous and liberal view that Solomon was not the author of Ecclesiastes.