Amazon is currently running a "buy three from this list, pay for just two" sale, which has a good number of Tolkien items in it:

https://www.amazon.com/promotion/psp/ANQ8E78JXZ53U?ref=psp_pc_atc&redirectAsin=0618512659&redirectMerchantId=ATVPDKIKX0DER

I do not know how long this promotion will be running, but there are some great prices at the moment (even before the free book offer)

This site uses affiliate links for which we may be compensated
Letters From Father Christmas
Tolkien, J.R.R.
0618512659
(Paperback)
$11.66
Availability: Now
Check at Amazon.com

This site uses affiliate links for which we may be compensated
The Silmarillion: Illustrated by J.R.R. Tolkien (Tolkien Editions) (Tolkien Illustrated Editions)
Tolkien, J. R. R.
0063280779
(Hardcover)
$39.78
Availability: Now
Check at Amazon.com

This site uses affiliate links for which we may be compensated
J.R.R. Tolkien 4-Book Boxed Set: The Hobbit and The Lord of the Rings
Tolkien, J.R.R.
0345538374
(Mass Market Paperback)
$16.58
Availability: Now
Check at Amazon.com

This site uses affiliate links for which we may be compensated
Pictures by J.R.R. Tolkien
Tolkien, J. R. R.
0358653045
(Hardcover)
$19.29
Availability: Now
Check at Amazon.com

This site uses affiliate links for which we may be compensated
Tolkien Fantasy Tales Box Set (The Tolkien Reader/The Silmarillion/Unfinished Tales/Sir Gawain and the Green Knight)
J.R.R. Tolkien
0345466462
(Mass Market Paperback)
$27.26
Availability: Now
Check at Amazon.com

This site uses affiliate links for which we may be compensated
The Making of Middle-earth: The Worlds of Tolkien and The Lord of the Rings
Snyder, Christopher A.
1454944757
(Hardcover)
$20.30
Availability: Now
Check at Amazon.com

This site uses affiliate links for which we may be compensated
The Complete Tolkien Companion
Tyler, J. E. A.
9781250023551
(Kindle Edition)
$14.99
Availability: Now
Check at Amazon.com

This site uses affiliate links for which we may be compensated
The Art Of The Lord Of The Rings By J.r.r. Tolkien
Tolkien, J.R.R.
0544636341
(Hardcover)
$21.99
Availability: Now
Check at Amazon.com

This site uses affiliate links for which we may be compensated
A Hobbit, a Wardrobe, and a Great War: How J.R.R. Tolkien and C.S. Lewis Rediscovered Faith, Friendship, and Heroism in the Cataclysm of 1914-1918 – The Perfect Christian Father's Day Gifts for Dad
Loconte, Joseph
0718091450
(Paperback)
$10.99
Availability: Now
Check at Amazon.com

This site uses affiliate links for which we may be compensated
J.R.R. Tolkien: A Biography
Carpenter, Humphrey
0618057021
(Kindle Edition)
$14.24
Availability: Now
Check at Amazon.com

This site uses affiliate links for which we may be compensated
The Languages of Tolkien's Middle-Earth: A Complete Guide to All Fourteen of the Languages Tolkien Invented
Ruth S. Noel
0395291305
(Paperback)
$10.89
Availability: Now
Check at Amazon.com

This site uses affiliate links for which we may be compensated
The Epic World of Tolkien: A Coloring Book
Editors of Thunder Bay Press
1645174581
(Paperback)
$9.49
Availability: Backorderable
Check at Amazon.com

This site uses affiliate links for which we may be compensated
John Ronald's Dragons: The Story of J. R. R. Tolkien
McAlister, Caroline
1626720924
(Hardcover)
$13.99
Availability: Now
Check at Amazon.com

This site uses affiliate links for which we may be compensated
The Fellowship: The Literary Lives of the Inklings: J.R.R. Tolkien, C. S. Lewis, Owen Barfield, Charles Williams
Zaleski, Philip
0374536252
(Paperback)
$13.49
Availability: Now
Check at Amazon.com

This site uses affiliate links for which we may be compensated
On the Shoulders of Hobbits: The Road to Virtue with Tolkien and Lewis
Markos, Louis
0802443192
(Paperback)
$14.39
Availability: Now
Check at Amazon.com

This site uses affiliate links for which we may be compensated
A Secret Vice: Tolkien on Invented Languages
Tolkien, J. R. R.
000834809X
(Hardcover)
$26.99
Availability: Now
Check at Amazon.com

This site uses affiliate links for which we may be compensated
J.R.R. Tolkien: Artist and Illustrator
Hammond, Wayne G.
0618083618
(Paperback)
$23.49
Availability: Now
Check at Amazon.com

This site uses affiliate links for which we may be compensated
Tolkien and the Study of His Sources: Critical Essays
0786464828
(Paperback)
$19.99
Availability: Now
Check at Amazon.com

This site uses affiliate links for which we may be compensated
Understanding The Lord Of The Rings: The Best of Tolkien Criticism
Isaacs, Neil D
0618422536
(Paperback)
$12.99
Availability: Now
Check at Amazon.com