I can make some recommendations! My main area of knowledge here is about the khipus, the Inca writing system using knotted cords. The khipus, as you may already be aware, were most famously used by the Inca. However, they are thought to have originated in the Wari period, and their use continued in parts of the Andes until the mid-20th century. (Even today, some are used for religious and ceremonial purposes, but there is no one alive today who is known to be able to read a khipu.) There have been a lot of exciting developments in the study of khipus in the past 10 years, many of them by Sabine Hyland (University of St Andrews). If you have access to academic articles via an institutional subscription, you can find her works here: https://risweb.st-andrews.ac.uk/portal/en/persons/sabine-patricia-hyland(3b30ab9c-2407-4965-9926-bcc0ad1b0477).html. Some of them are available on Academia.edu.

If you're not able to access research articles, her research has also been covered in online magazines which overall provide very good coverage of her work. (I can vouch for it as... I'm her daughter and know which ones she finds representative!) These appear in publications like National Geographic, Slate, Sapiens, Discover Magazine, Scientific American, and New Scientist. You can find links to them on her Wikipedia page. If you are based in the UK, you should also be able to listen to a radio interview she gave about her work with the BBC World Service. She was also interviewed with one of her PhD students who works on khipus for a German radio station.

Aside from khipus, she's worked on other aspects of Andean religion. I'd recommend three of her books in particular: The Jesuit and the Incas: The Extraordinary Life of Padre Blas Valera, S.J. (2003). This is about Blas Valera, a mestizo Jesuit who was persecuted by other Jesuits for arguing that the Inca religion should be kept as much as possible in the transition to Christianity.

Gods of the Andes: An Early Jesuit Account of Inca Religion and Andean Christianity (2011). This one I've actually read in full because I proofread it, haha. It's a translation of a text, possibly by Blas Valera, about the Inca religion. It's written by someone who wasn't that far removed from it at all, so it's a really valuable resource. I can vouch for its readability because when I proofread it, my mom asked me to make sure that her long introduction about Inca religion and the translation itself were accessible for introductory college courses.

The Chankas and the Priest: A Tale of Murder and Exile in Highland Peru (2016). This one I haven't actually read because it's about a rather gruesome and sadistic priest, but it's gotten a lot of attention as a gripping account of the Chanka, whose history has been seriously neglected. In 2004, my mother was recognised as an honorary member of the Chanka Nation by its then-leader, Miguel Suarez Contreras, in recognition of her contributions to the study of their people. The University of St Andrews put together a webpage with interviews my mom gave about the Chanka to coincide with the release of this book.

I can also recommend some resources about the Wari and Tiwanaku Empires, both of which predate the Inca. In the early 21st century there was a very exciting archaeological find on Pariti, and island in Lake Titicaca, with beautifully made pottery. You can read about it in this book: Pariti: The Ceremonial Tiwanaku Pottery of an Island in Lake Titicaca by Antti Korpisaari and Martti Pärssinen (2011) link. There is also coverage of the finds in popular articles here and here.

A good book about the holy islands in Lake Titicaca in general is Ritual and Pilgrimage in the Ancient Andes: The Islands of the Sun and Moon by Brian S. Bauer and Charles Stanish (2001). They mainly focus on the Inca period and talk a lot about what archaeology can tell us about the pilgrimage centres there.

There have also recently been some great publications about Wari excavations at Castillo de Huarmey, where they found a royal tomb with dozens of finely dressed elite women. There were even some khipus there which Gary Urton has offered some great analysis of. You can read that and other essays about the finds in Castillo de Huarmey: El Mausoleo Imperial Wari (2014, Asociación Museo de Arte de Lima). (A lot of the essays are available online in English and Spanish if you poke around Academia.edu.) If you're not able to access those, there was some coverage of the finds in National Geographic here and here.

Finally, my personal favourite book about the Andes is Art of the Andes by Rebecca Stone-Miller. It's got a great overview of art and architecture from the earliest days of Andean art through the Inca.