The Rare Book & Special Collections Reading Room of the Library of Congress holds a number of rare books of Bulgarian origin, including those in the crown jewel of the Bulgarian collections, the Early Bulgarian Imprint Collection. Amassed by the private collector, Todor Plochev, the collection was purchased by the Library of Congress in 1949. It consists of approximately 650 books and serials published between 1806-1878, the so-called National Revival era in Bulgarian history, when the Bulgarians strove to attain their political independence from the Ottoman Empire and their religious and cultural autonomy from the Greeks. Most of the books from this time period were published outside the territory of contemporary Bulgaria due to Ottoman restrictions on printing in Cyrillic.

The Early Bulgarian Imprint collection has titles on a range of subjects from religion and grammar to history and literature. Notable works in the collection include Kyriakodromion [Sunday Book] (1806), a book of sermons written by Sofronii Vrachanski. This book is considered to be the first book published in modern Bulgarian, although its language was still reminiscent of Church Slavic. Original editions of Neofit Rilski's Bolgarska grammatika [Bulgarian grammar] (1835) and Petur Beron's Bukvar s razlichny poucheniia [Primer with various instructions] (1824), the first Bulgarian grammar and the first Bulgarian primer, are both in the collection, as are later works reflecting the development of language study in Bulgaria. Also present are first editions of literary works by Petko Slaveikov, Liuben Karavelov, and Georgi Rakovski, among others.

Besides Bulgarian literature, the collection contains translations into Bulgarian of notable world authors such as Molière, Hugo, Defoe, and even Benjamin Franklin. Textbooks were a popular and necessary genre during this time period, for the Bulgarians were trying to increase literacy in the Bulgarian tongue and provide general education for the people, thus the collection contains many on geography, history, the Bulgarian language, foreign languages, and literature. An interesting example is Khristiaki Dupnichanin's Pismennik obshchepolezen na sekogo edinorodnago mi Bolgarina ot koi i de e chin i vozrast' [Letterbook of general use for each of my fellow Bulgarians of every rank and age] (1835), which instructs the reader on the proper way to write letters and invitations. For a detailed survey of the Early Bulgarian Imprint Collection, see the article "Bulgarian Incunabula" by Charles Jelavich in the section of this guide entitled "Publications by the Library of Congress on Bulgaria." An online guide devoted to the Early Bulgarian Imprint Collection is forthcoming in 2023.

A landmark work of interest to all of the South Slavic nations is the original 1601 printing of Il regno degli Slavi hoggi corrottamente detti schiauoni [Realm of the Slavs] by Mauro Orbini (1550-1611), a Benedictine monk from Dubrovnik (Ragusa). Although Orbini incorporated unsubstantiated legends and chronicles, his history of the Slavs, with a special focus on the South Slavs, also relied on many other sources including works by Orthodox and Protestant writers which were banned by the Vatican, resulting in his work being banned as well in 1603.

Also in the Library of Congress Rare Book collection is the 1722 Russian translation of Orbini's history Knīga Istorīograḟīi︠a︡ pochatīi︠a︡ imene, slavy, i razshīrenīi︠a︡ naroda slavi︠a︡nskogo [Book of historiography on the origins of the name, glory and expansion of the Slavic people], translated by Sava Vladislavić (1669-1738), a diplomat from Herzegovina and Dubrovnik who served on behalf of the Russian tsar Peter the Great. Il regno degli Slavi and its Russian translation were of enormous significance for the historiography of the South Slavs and the Pan-Slavic philosophy.

Other rare Bulgarian books include the first Bulgarian books ever to be added to the Library's collection, translations of the Book of Genesis (1857), the New Testament (1850) and a psalter (1857), in the Bible Collection. Selected titles from the 20th century are a framed broadside replica of the Turnovo constitution presented in 1954 by émigré members of the Union of Bulgarian Jurists, and an autographed reprint of Fashizmut [Fascism] by Zheliu Zhelev, a Bulgarian dissident who became the first democratically elected president of post-communist Bulgaria. All materials held by the Rare Book and Special Collections Reading Room must be used onsite, unless there happens to be a digitized version on the Library of Congress website.