Some Italian public libraries (e.g., Biblioteca Digitale Italiana , MediaLibraryOnline ) offer e-book lending. Register for free with a library card (some accept non-residents). Borrow the e-book for 14–30 days.
However, the legality of these downloads is the core issue. Grammatica Italiana Luca Serianni Download
"Grammatica Italiana" by Luca Serianni is widely available online. You can download the textbook from various sources, including: Some Italian public libraries (e