Are all ancient books written in traditional Chinese characters? Where can I read the traditional version?

Of course, ancient books are written in traditional Chinese characters, and simplified Chinese characters have only appeared for decades, but books written for decades are not ancient anyway, right? As for reading, it is rarely seen online, and most of them are stored in the library after scanning. You may have to pay to watch them. The physical Xinhua Bookstore will have it, but the stock is estimated to be small. Of course, you can buy it if you are interested. I have several books at hand, such as Tao Te Ching, Sun Tzu's Art of War and Zhuangzi, but I have a headache. After all, I can't recognize all the traditional Chinese characters.