I'm finishing my third year of biochemistry and doing gene therapy practicals during the summer. I'd like to buy a book that describes flow of genetic information (transcription, translation, replication, splicing...) and its mechanisms in depth (such as transcription factors, regulation, etc). The closest thing I currently own is Lehninger's Principles of Biochemistry, but most of it deals with metabolism. I've also got to know about Molecular Biology of the Gene, but I'm not sure if it's what I'm looking for. I'm not interested in books about heredity or population genetics.
Molecular Biology of the Cell is a great text book, and an older edition is available for free on NCBI bookshelf. However, the book covers a broader range of topics than perhaps you're interested in and may not go into the same depth as others (though I haven't actually done a side-by-side comparison).
Watson, who along with Crick developed the central dogma of molecular biology, literally wrote the book on this subject: Molecular Biology of the Gene. It sounds exactly like the text book you’re looking for, and was one of my favourites as an undergrad. You can check out the contents of the book yourself to make sure it's what you want.
The classic, "The molecular biology of the cell" https://en.wikipedia.org/wiki/Molecular_Biology_of_the_Cell_(textbook) helped me a great deal...30 years ago. It has been continually updated and is the best source I know. However, books take years to write, and are therefore always years behind. With answers to every imaginable question on the internet, why limit yourself to books?