@kassandra Hi,
I would like to share with you the way I achieved IELTS 8.0 in 3 months.
For improving my vocabulary, I chose English Vocabulary in Use (upper-intermediate), English Collocations in Use
For Grammar, I learnt a lot from this excellent book: English Grammar in Use by Raymond Murphy, Advanced Grammar in Use
For Reading, I polished up my Reading skills by reading articles from Your IELTS Reading Skills by Sam McCarter, practicing IELTS Reading Recent Actual Test Vol 1, 2
For Writing, I'm a fan of these books: Improve Your IELTS Writing Skills by Sam McCarter, Write Right and Visuals by Gabi Duigu. I learnt most from this blog: ieltsmaterial.com for IELTS Writing Task 2 (& I got 8.0 for Writing)
For Listening, I chose IELTS Listening Recent Actual Tests Vol 1,2
For Practice Tests, I downloaded Cambridge series 1- 10 and practiced every single day
For IELTS tips, strategies and guides, I highly recommend IELTS Target Band 7: How to maximise your score and The official cambridge guide to IELTS , new insight into IELTS
These books are shared by a lot of IELTS bloggers, IELTS teachers. You can google these books to read more reviews about them. Most of the mentioned books, I downloaded from this useful website: http://Ieltsmaterial.com
Hope my sharing can help you somehow 🙂