smiddy3, actually the book study format was really the first meeting, studying Russell's Studies in the Scriptures in small groups in homes. The WT was not a study publication, that did not come later.
https://wol.jw.org/en/wol/d/r1/lp-e/301975003#h=159:0-159:177
Meetings of the Bible Students continued to supply rich spiritual food. Group studies of The Watch Tower were first organized in 1922.
https://wol.jw.org/en/wol/d/r1/lp-e/1102014255
The June 15, 1932, Watchtower provided further direction on how this meeting should be conducted. Using as a model the study that was conducted in the Bethel Home, the article stated that a brother should lead the meeting. Three brothers could sit at the front of the meeting place and take turns reading the paragraphs. Articles at that time did not include printed questions, so the conductor was told to ask the audience to raise questions on the material under consideration. After that, he would call on people in the audience to give answers to those questions. If further clarification was needed, the conductor was directed to offer a “brief and succinct” explanation.
https://wol.jw.org/en/wol/d/r1/lp-e/2007322#h=16:0-16:503
At that time (1935) the group of Witnesses with whom we associated met as a congregation in Fort Dodge, Iowa. Much effort was required to attend Christian meetings. Back then, the Watchtower study articles did not include questions for the congregation discussion. We were asked to submit prepared questions to the brother who conducted the Watchtower Study. On Monday nights, my mother and I prepared a question for each paragraph, and we gave these to the conductor so that he could choose which ones to use.
Rutherford gradually phased out the Studies letting them go out of print and substituting his own books as vehicles of learning. Early on in the WTS history, members were told that they could only understand the bible through the WTS and its publications. Studying the bible by itself and by themselves would not lead them to the truth.
"Furthermore, not only do we find that people cannot see the divine plan in studying the Bible by itself, but we see, also, that if anyone lays the SCRIPTURE STUDIES aside, even after he has used them, after he has become familiar with them, after he has read them for ten years - if he then lays them aside and ignores them and goes to the Bible alone, though he has understood his Bible for ten years, our experience shows that within two years he goes into darkness. On the other hand, if he had earnest heed to the opportunities for service and consider that merely read the SCRIPTURE STUDIES with their references, and had not read a page of the Bible, as such, he would be in the light at the end of the two years, because he would have the light of the Scriptures." Watchtower 1910 Sep 15 reprints p.344