These are the books I most frequently use when doing a genealogical research. Some are available online, but most can be found in libraries or purchased from second-hand book sellers.
1. Latvian Surnames in Archive Materials (Latviešu uzvārdi arhīvu materiālos). This research, led by I. Mežs, and publication by the Latvian Language Agency, was released in several volumes from 2017-2022 and is now also available as a database at uzvardi.lv
Here you will find:
How many people with a specific surname were registered in Latvia in 2020?
In which parishes was the surname registered in 1935, sometimes including references to older sources?
Explanations of the meanings of surnames
Be sure to also read the introductions that explain the history of surnames in each of the historical lands. Both the book and the website are in Latvian, but with modern technological tools, you will hopefully be able to translate the information you need.
2. Latvian Personal Names Dictionary (Latviešu personvārdu vārdnīca, K. Siliņš, Zinātne, 1990).
It provides explanations about the origins of personal names, explaining from which word and language it derived, when and where it was first mentioned, and even statistical data on the name's prevalence.
3. Latvia in the 19th Century: Historical Essays (Latvija 19. gadsimtā. Vēstures apceres, Editor J. Bērziņš, Latvijas Vēstures institūta apgāds, 2000). This book provides Latvian genealogists insights into the historical context:
What life was like for peasants and city dwellers in the 19th century?
What laws were adopted and how they changed life?
What institutions regulated life? This sometimes helps to understand which institution's archives might hold certain information.
4. Index of Riga's Streets, Squares, Parks, and Bridges (Rīgas ielu, laukumu, parku un tiltu nosaukumu rādītājs, editor A.J. Zālīte, Rīga, 2000). This is an index for researching the historical names of Riga's streets. Previously, streets had names in German and Russian as well, and these were translations, not just transliterations. For example, Krāsotāju Street was called Färberstrasse in German and Красильная улица in Russian.
This index is indispensable when looking for information in house books. Part of this information is also available on Ciltskoki.lv (Palīgs>Rīgas ielu agrākie nosaukumi).
5. The Borders of Latvian Lands Over 100 Years (Latvijas zemju robežas 100 gados, compiled by A. Caune, Latvijas Vēstures institūta apgāds 1999).
In this book, I look for information when I need clarification on which parish a place belonged to. To know which parish archive to search in, it's necessary to know to which manor and later which civil parish certain farms belonged. Of course, historical maps found online at vesture.dodies.lv and kartes.lndb.lv are also a great help.
6. From NKVD to KGB (No NKVD līdz KGB, editors R. Vīksne, K. Kangeris, Latvijas Vēstures institūta apgāds 1999) .
I recently described this criminal case index in a blog post, but I want to mention it again. I use it quite frequently to check information about people whose fates after World War II are unknown.
7. Aid for German Script Paleography in Latvian Archives and Libraries from the 16th to the Early 20th Century (Palīglīdzeklis Latvijas arhīvu un bibliotēku 16.gadsimta – 20. gadsimta sākuma vācu rokrakstu paleogrāfijā, compiled by M. v. Boetticher, E.Rubina, K. Zvirgzdiņš, Latvijas Nacionālais arhīvs, Latvijas arhīvistu biedrība 2018). This appears to be the first and only educational material in Latvian on reading historical German script. Although it is not specifically designed for genealogists and unfortunately does not cover church books or soul revision records, it does explain the development of German script. Examples of manuscripts from Latvian Historical Archive and their transcriptions are examined.
Of course, these are not the only books useful for Latvian family researchers, but merely a small selection! Each researcher will certainly have additions, especially if focusing on a specific place or period.