I have been searching for the title of a TOS-TNG crossover novel for some time. I believe it was published in the early 1990s, as I do not remember Voyager or DS9 being on TV. It was also before ST:Generations was made. I know it is not the novel Star Trek: Federation, as the two crews actually work together and meet one another. Also, I seem to remember that the front cover said something to the effect of, "at last, the generations meet!"