Since the difference between hardback and softback is the kind of cover and binding, being the former more expensive and precious, I propose:
Is hardback of this book available? = Questo libro è disponibile in edizione rilegata (con copertina rigida)?
Is hardback, first edition of this book available? = E' disponibile la prima edizione di questo libro in versione rilegata (con copertina rigida)?
Please be aware that, in this case, the first edition is not necessarily a hardback book, so they would supply you with the first edition as hardback
Is softback edition in a very small print? = l'edizione economica è in caratteri molto piccoli?
Is softback edition in a very small print? = l'edizione economica è in caratteri minuscoli?
I hope this helps. Let me know if you have further questions.