I know it was written more than ten years later, but Shadows of the Empire addresses most of those issues you brought up, Shadowheart. According to that, they had quite a bit of contact, and planned it all together. At the end of Shadows of the Empire, Luke is at Ben's old place recording the message for Jabba, Leia and Chewie are off together on their way to Jabba, and Lando had gone in sometime before. I suppose Shadows of the Empire has slightly more credit to it than your average EU, since Lucas was more involved in it. It wasn't just one book planned and written by a single writter, but a multimedia project including an action figure line and even a sound track. Also the fact that Dash Render's ship The Outrider makes a cameo appearance in the SE of ANH also seems to give more weight to it than your average EU. A lot of people hated Shadows, I loved it. The book may have not been the best written, but the story was great and really flowed well with the OT so well that if you didn't know any better you might think ROTJ was written after it. The PT couldn't even manage to do this.

For anyone who has not read Shadows of the Empire, I'd highly recomend going to your public library and picking up the audio book. It is well read, and the abridgment actually improves on many of the novel's weak points. To me, the audio book is the definitive version of SOTE. The video game was pretty awesome too, but the N64 graphics are very dated today.