Kemp, Franz Hermann - "Chronik Thelen-Herhahn-Katterbach - Die Familien Thelen-Borgs-Katterbach und Herhahn", Bonn, 1956 und Rübens, Dr. Frida - Ahnenliste Rübens; Teilahnenliste aus der Ahneliste Nierstras-Rübens. Aufgestellt von Dr. Frida Rübens, Christinastr. 2a, 5630 Remscheid, Fed. Rep. of Germany basierend auf den Kirchenbücher der betreffendedn Orte; Chronik der Familie Thelen, Bonn 1956; Arbeiten von Dr. Josef Roelen; Dr. F.W. Lohmann " Der Weltklerus in den Kölner Erzbistums-Protokollen 3 Bände, Köln 1936"; Stommerl, Karl - "Die Mellerhöfe", vergl. auch Deutsche Ahnenreihen Westdeutsche Gesellschaft für Famlienkunde e.V., Sitz Köln, Heft I bis VI Nº 1-296 bearbeitet von Max Franz Joseph Reichsfreiherr Raitz von Frentz, Bad Godesberg (1925-1934), Nachdruck 1990
 Basqué, Norbert Josef - Stammbaum der Familie Esser, Thelen, Dohmen & Basque usw., Bonn, 1993, ungedruckt
 Kemp, Franz Hermann - Die Familien Thelen-Borgs-Katterbach und Herhahn, Bonn 1956
The 1928 book was written by Carl Thelen entitled the Chronik Thelen, 1550-1928 as best I recall.The 1956 book by Kemp builds upon the 1928 book and has information on related families such as Kemp, Stassen, Bardenheuer, Katterbach, Conzen, Hons, Herhahn, Breuer and others.Some corrections were also made.
These books cover a small percentage of the total Thelens in the U.S.These particular Thelens immigrated to the U.S. in the early 1870's to Polk County, Nebraska.Later a few came from Germany to Boston, MA.
A fair percentage of the Nebraska Thelens remained there with some moving to California beginning with Edmund in 1887 and later Ernst.They settled in the San Diego area originally.Edmund's family fanned out to San Francisco Bay Area (Max) and to Wisconson (Rolf T.).For a while a Gustav Thelen was in Oklahoma but evidently returned to Nebraska.One son had an agricultural business in Wyoming.
I have no recent data on the Thelens in Massachussetts but assume they fanned out to other areas in the East.
Most of the Thelens in this family remained in Germany.They are primarily found in the Niederrhein (upper Rhine area below Westphalia) area above what is the Rheinland Pfalz (Bonn, Aachen, Koeln, Monchengladbach and Neuss) currently.The early Thelens were found in Kreis Euskirchen and Kreis Dueren starting in the village Stockheim.
In doing research there were other separate unrelated families in the 1600's (at least as far as is known to 1590) further South in the Pfalz, in Bonn and Koeln, North near Duisberg and Dusseldorf and even further North in Westphalia.There were some Thelens near Aachen in what is present day Belgium and at least one family in Northern Netherlands in 1658.There were also Ritter (knights) von Thelens in the early 1600's in Monchengladbach and Koeln (Cologne) and Westphalia.
If one looks they will find Thelens in Finland starting in 1759.I believe a number of German families settled there but know not why.The name emerges in Sweden in the late 1700's but in looking at the parents names neither of which is Thelen I can only figure there is no relationship to German Thelens
If one checks German Name Lexicon books generally the name is believed to have emerged around 1600 in the Rheinland and Westphalia.I believe it is much older.There are records of people with the surname Thelen dating to the 1580's and an instance of the name used as a first name in 1477 in Heidhausen near Essen.
So, in summary the books may cover your Thelen research interests if they come from the areas and time frames mentioned.