The real trick is knowing that the term 'silent novel' is often misapplied. There's no single genre with that exact name. It might be used in fan circles to mean a novelization without dialogue, or a text-heavy piece that evokes silence through atmosphere, but it's not an official bookstore category. Legally accessing niche content online for free means leaning heavily on public domain sources and author-endorsed promotions.
Project Gutenberg is a logical first stop for classics that might fit the 'silent' mood—think something like 'The Great Stone Face' by Nathaniel Hawthorne, which is more descriptive narrative. For contemporary stuff, authors sometimes release short stories or early works for free on their personal blogs or sites like Wattpad to build an audience, using tags like 'atmospheric' or 'minimal dialogue.' Serial platforms like Royal Road often have trending stories with a heavy emphasis on internal monologue and description over chatty characters.
You might have more luck searching by the feeling you want—'atmospheric novel,' 'descriptive prose,' 'minimal dialogue'—and then checking if those specific titles have free samples on Amazon Kindle, Google Books, or the publisher's site. I found a fantastic, nearly wordless graphic novel prologue once just on an artist's Tumblr, which was a legal freebie to promote the full book.