Sikhs have made a lot of history but have failed to accurately record it. The modern history recording techniques and methodology was not available when Sikh historical texts were written and for this reason, these texts e.g. Sooraj Prakash, Pracheen Panth Prakash etc. contain few errors and some mythology as well.
Modern Sikh historians from Sardar Karam Singh Historian to Principal Satbir Singh have written Sikh history based on the few aforementioned historical texts. Sardar Karam Singh has written that he wishes to kiss the hands of Sardar Rattan Singh Bhangu, who wrote Pracheen Panth Prakash. Even though this Granth has many errors but still we would have never known about Shaheed Bota Singh, Shaheed Tara Singh Vaan, Shaheed Mehtab Singh and Shaheed Sukha Singh who cut the head of Massa Rangadh in such a dashing way. By the same token, this Granth also sowed the seeds of disdain towards our best and first General - Baba Banda Singh jee Bahadur.
Similarly, the Sooraj Prakash Granth, written by the legendary poet, Mahakavi Santokh Singh jee Chooramani, contains some errors and exaggerated material, but still with the absence of this Granth, a lot that we know about our Guru Sahibaan, would have been unknown to us.
We should not call Mahakavi jee and Sardar Rattan Singh jee pure historians but what they did was that they recorded anything event or Saakhi they heard about Guru Sahib, without any bias and left the task of deciphering Gurmat from Manmatt, to the future historians. I think this was a wonderful thing they did. If they had started filtering out Saakhis they collected by traveling village to village, they would have possibly left out some real and genuine Saakhis and this would have been a great loss for us. We can't imagine not knowing even one Saakhi of Guru Sahib.
Bhai Vir Singh jee is not known to be a pure historian because he wrote our history not from pure historian's point of view but wrote it from a devout Sikh's point of view. The wonderful thing is that while writing history this way, he tried not to ignore the facts and quite often backed his claims with references. Having said that, he did make some judgmental errors e.g. writing about meat being served in the Langar of Siri Guru Angad Dev jee, and thus blindly following Sooraj Prakash Granth.
Dr. Ganda Singh is said to be one of the best historians of Sikhs because while he employed modern methodology while writing history, he was a very Sikh-minded person who did not let his opinion get biased by reading non-Sikh references to our history. He collected a lot of references from Farsi sources and these have been very helpful in writing our history. Some of his best books are on Baba Banda Singh, Sardar Jassa Singh Ahluwalia, and Kooka movement. He has covered about 100 years of history in the first two books. His third book mentioned above is a very good book that presents a very unbiased view of Baba Raam Singh jee Namdhari.
Principal Satbir Singh has written Sikh history with both Shardha and correct facts. There are some errors in his writings e.g. he writes about Sardar Ala Singh taking Amrit from Nawab Kapur Singh, instead of saying Punj Pyare including Nawab Kapur Singh but we can ignore such errors as they are not material. He has written a history book on each of our Guru Sahibaan. Furthermore, he wrote the history of Sikhs post Guru period. He has written some wonderful books that are a must for the serious reader.
Couple of decades ago, Sardar Sarvan Singh's historical writings used to appear in the Soora magazine and then he also published some books e.g. Bhai Tara Singh Vaan, Massa Rangad etc. but we did not hear much from him afterwards. He was a very promising historian who should have written more. His serial article on history had a very interesting name - ਭੂਰਿਆਂ ਵਾਲੇ ਰਾਜੇ ਕੀਤੇ, ਮੁਗ਼ਲਾਂ ਜ਼ਹਿਰ ਪਿਆਲੇ ਪੀਤੇ।
My first book on Sikh history and written in Punjabi, was a book called "Sikh Kithon taun Kithay". I read this when I was about 12-13 years old. This book contains complete history of Sikhs concisely but not too tersely. It's got just enough to get you aware of the proud Sikh history. I recently saw that a new edition of this book has come out. I think this is an excellent book for a beginner.