There were many books written in the 18-19th century which provided practical halachic guidance for the layperson. The Shulchan Aruch had become so covered with commentaries that it was no longer easy to actually know what to do and what not. So in Europe we find books such as Shulchan Aruch Harav, Aruch HaShulchan, Kitzur Shulchan Aruch and the most famous the Mishna Brura. In the Sefardi world there was the Ben Ish Chai and the Kaf HaChaim and Makor Chaim.
The standard 'text book' for Lithuanian Jewry was the Chay Adam on daily living (Orech Chaim things) and Chochmas Adam on other issues (Yoreh Deah things - Chochma/ Deah). His rulings even today carry more weight for real 'Litvaks' than the Mishna Brura (at least some times).
He is also the author of several other little known but excellent Halachic works (listed below). Most of them have been reprinted in the latest edition of the two 'Adams'. Learn them!
Here is the bio from the Jewish Encyclopedia:
AVRAHAM BEN YECHIEL DANZIG
Lithuanian codifier; born in Danzig in 1747 or 1748; died at Wilna Sept. 12, 1820. He was descended from a family of scholars in West Prussia, his great-grandfather, Jehiel Michael, having been rabbi in Schottland, near Danzig; his grandfather was Samuel, the author of the commentary on Isaiah, "Neḥamot Ẓiyyon." When Danzig was fourteen years old his father sent him to the yeshibah in Prague, after exacting from him a promise that he would not mingle with the "Moderns," who, through the influence of Mendelssohn in Prussia, were gradually coming into prominence. Under the guidance of Ezekiel Landau and Joseph Liebermann, Danzig zealously devoted himself to the study of the Talmud, and at eighteen years of age he left Bohemia with a "ḥaber" diploma, showing him to be a proficient Talmudist. He then settled in Wilna, Lithuania. When offered the salaried position of rabbi he declined it, considering it improper to receive a stipend in such a capacity, and he engaged in business as a merchant, visiting the fairs of Leipsic and Königsberg. Only in his later years, and after having lost almost his entire fortune through the explosion of a powder-magazine, could he be induced to accept the position of dayyan in Wilna, which office he held until his death. His fixed intention had been to emigrate to the Holy Land.
Danzig is the author of the following: "Ḥayye Adam: Nishmat Adam" (The Life of Man: the Soul of Man), Wilna, 1810, reedited many times; "Ḥokmat Adam: Binat Adam" (The Wisdom of Man: the Understanding of Man), ib. 1814, reedited many times; "Sha'are Ẓedeḳ" (The Gates of Justice), on the commandments and prohibitions having reference to the land of Palestine, ib. 1812; Jerusalem, 1863. "Zikru Torat Mosheh" (Be Mindful of the Teaching of Moses), precepts for the Sabbath, Wilna, 1820, and several editions (this little work contains by way of supplement the treatise "Miẓwot Mosheh" [The Precepts of Moses], an extract from Askari's book "Ḥaredim" [The God-Fearing]; "Toledot Adam," a commentary on the Passover Haggadah, ib. 1817 (in the Haggadah edition "Ma'aleh Bet Ḥoron"); "Bet Abraham" (The House of Abraham), his last work, 1821, and many editions (also translated into Judæo-German by Isaac Hamburger, Lemberg, 1875). Among the writings of Danzig not yet published are an elaborate ethical work, specimen pages of which are contained in the introduction to "Zikru Torat Mosheh," and commentaries to several books of the Bible.
Danzig is especially known as the author of "Ḥayye Adam" and "Ḥokmat Adam," which represent the most important productions in the line of codification after the time of Joseph Caro and Mordecai Yafe. In these two works Danzig treats of the same subject-matter as the first two parts of the Shulḥan 'Aruk. The enormous mass of new material which had accumulated in the field of the Halakah since the appearance of the Shulḥan 'Aruk—a period embracing more than two and a half centuries—was collected and critically sifted by Danzig and presented in a readily intelligible form. His codex, however, was intended primarily for the cultured layman and not for the officiating rabbi. Hence there is a tendency to give prominence to the more exacting side of the Law, even though in his expert decisions and treatises, which, under the respective titles of "Nishmat Adam" and "Binat Adam," are added to "Ḥayye Adam" and "Ḥokmat Adam," Danzig shows independence enough to oppose the views of the AḤaronim, and he frequently protests against the tendency to decide in favor of new prohibitions. His "Ḥayye Adam" met with unusual success during the author's lifetime. In many cities societies were formed for the purpose of studying this work; and even to-day these societies may be found in most of the Polish-Russian communities.
His Importance as Codifier.
This success was well merited; for there is hardly another work that presents in so concise and lucid a manner all the details of the discussions of the Aḥaronim. Danzig preserves in his works a certain freshness of tone, and dwells with special emphasis upon the ethical bearings of religious precepts. The high ethical standpoint of the author reveals itself most conspicuously in his "Bet Abraham," and the contents of this little book alone should suffice to refute the accusation that Talmudism had stitled religio-ethical sentiments. The love of God, it is pointed out, is man's highest mission, to which the fear of God is only a preparatory stage. The enjoyment of worldly things is not in itself to be condemned; but man is to bear constantly in mind that the recognition of God and the exercise of good deeds are the proper occupation of life. He lays great stress upon prayer; but this must not bemere lip-service; and, accordingly, he bids his children say their prayers in German rather than in unintelligible Hebrew. This is all the more noteworthy since Danzig in this very work enters a protest against all innovations, and even denounces the reading of German books.
Love of truth and contentedness he especially enjoins; and declares repeatedly that "an offense against one's fellow being is far more reprehensible than a sin against God." He not only admonishes his family, therefore, to refrain from all dishonesty in their business relations with both Jews and non-Jews, but makes it a duty never to decide in money matters according to one's own opinions, but to inquire of a learned man whether the intended action conforms to the Law. While insisting upon the strictest observance of the rites, he bids his children even to let the time of prayer pass if this be necessary to secure money wherewith to pay a working man's wages.
Characteristic of Danzig is his warning not to study the Cabala before the age of maturity and before the study of the Talmudic-rabbinic literature. He himself shows an acquaintance with the Cabala; but in his halakic writings this is not made apparent. A somewhat mystical touch appears in his prayer for the eve of the Day of Atonement. This prayer may be found in "Ḥayye Adam" (No. 144), and has been published separately several times in Judæo-German as well as in Hebrew, under the title "Tefillah Zakkah" (Sincere Prayer).
May His Soul be Bound in the Bonds of Eternal Life