I think it is true that Marlene (not Marilyn) Silverman obtained data from some sources that could not be obtained elsewhere (e.g. from Galina Baranova of the Lithuanian archives), though I think subsequently most information did appear on JRI Poland and Litvak SIG. A lot of the usefulness of the journal Landsmen was from the articles on the Jewish history and geogaphy of the Suwalki Lomza area, and of the family histories of members of the SIG, which was very international in scope.
These sorts of articles can now be found in other journals e.g. Shemot the journal of the Jewish Genealogical Society of GB. The current Chair of the JGSGB has ancestors from the Suwalki Lomza area. However this is no substitute for a dedicated group, but it needed a lot of resources to organise, especially as it was paper rather than online based.
As this area was, and still is, a border area of NE Poland wedged between Kaliningrad (Koningsberg, East Prussia), Belarus and Lithuania, it had a paricular interest for many of us. Our ancestors were culturally Litvak (due to having been part of Lithuania in the middle ages) despite being situated in Poland (under Tsarist control) for most of the 19th and early 20th century.
Jill Whitehead nee Servian (Serwianski), Surrey, UK
Former UK rep on Landsmen editorial board