I also really like the Maxim Kammerer books about the Wanderers, the mysterious, incomprehensibly intelligent alien race that seems to be manipulating the human race from some unseen vantage point. The first novel in this sequence is "Beetle in the Anthill", and continues with "The Time Wanderers". A connection to Roadside Picnic is never made, but it's certainly possible to speculate.
(One of the novels you mention, "The Inhabited Islans", is also about Max, and was also published in English as "Prisoners of Power". There is a recent Russian movie adaptation of it that's apparently not bad -- anyone seen it?)
There is also a great short story, "Wanderers and Travellers", set within this same continuum. It can be found in the anthology "Paths Into the Unknown". It's a wonderful little gem for anyone who loves Roadside Picnic or the Wanderer novels, or just scifi in general.
(One of the novels you mention, "The Inhabited Islans", is also about Max, and was also published in English as "Prisoners of Power". There is a recent Russian movie adaptation of it that's apparently not bad -- anyone seen it?)
There is also a great short story, "Wanderers and Travellers", set within this same continuum. It can be found in the anthology "Paths Into the Unknown". It's a wonderful little gem for anyone who loves Roadside Picnic or the Wanderer novels, or just scifi in general.