Such questions are always difficult to answer because this highly depends on ones interests and biological and geological background. In the last fifteen years a wide variety of palaeobotanical text books has been published. Each author and each book has a different objective.
Some books concentrate on specific topics such as early land plants or the earliest angiosperms.
A number of recent text books are listed below in alphabetical order and some general comments are given. Origin and evolution of gymnosperms. Columbia University Press, New York. This book with contributions by recognized specialists in their field gives an excellent overview over gymnosperm development ranging from Devonian progymnosperms to the origin of modern conifer families. Unfortunately, the plates are rather small and the photographs sometimes a little bit greyish .