Please start with " Bioinformatics: a Beginners guide" by Jean micheal claverie and cedric notredame. If it is not available then Bioinformatics for dummies by the same authors is a very good book for newbies. If you are looking at a particular aspect of Bioinfo please mention.
I'm surprised no one recommended "Introduction of Bioinformatics" by Arthur M. Lesk which is a pioneer in the field. I believe a new edition was published this year.
For detailed illustration of a variety of bioinformatics algorithms and applications, you may find my book "Bioinformatics and the cell: modern computational approaches in genomics, proteomics and transcriptomics" (Springer 2018 2nd edition) better than others. It can be accessed through SpringerLink at Book Bioinformatics and the Cell
The truth is when people hear the word bioinformatics, what comes first is computational scripting, which is wrong. First learn the basics of molecular biology, genomics and proteomics. Then you proceed with sequence alignments, blasts and the rest. So it's a gradual process. Don't rush it.
I use "Bioinformatics for Beginners" by Choudhuri for my undergraduate introductory course. It's a great reference to introduce the informatics context and the author nicely merges its use within a biological perspective. The reading is not difficult and the author includes some exercises within the text. It's a little old (2014), but many of the computational programs are still being used today. I've even used Choudhuri to supplement my master's course and has worked very well.
On a side note, I used "Introduction to Bioinformatics" by Arthur Lesk, but I found that it lacked readability for someone that is just starting out in this field. Also, Lesk doesn't give a basic introduction as to the history of bioinformatics, either.
This book might help you, Siku Biology . I am a Graduate student. I have learned many basic topics in this book. It is written quite an easy way, better for understanding for beginners.
Introduction to Bioinformatics 5th Edition, from Arthur M. Lesk, who is Professor of Biochemistry and Molecular Biology at The Pennsylvania State University, USA.
I recommend "Applied Bioinformatics" by Selzer, P. M., Marhöfer, R. J., Koch, O. published in 2018. ( ISBN 978-3-319-68301-0). It is an introductory book and also gives clear information for common bioinformatic tools.
If you want hopefully to learn the preliminary alphabet of bioinformatics and computational biology, I highly recommend you to read the attached book. It provides an excellent infrastructure for all biologists, biotechnologists, and even chemists and other enthusiasts to step forward towards all things you should know about the essence of bioinformatics.
The recommended books in the previous comments are nice choices whenever you get the primary aspect of computational biology first. So basically, please take a look at "Understanding Bioinformatics by Marketa Zvelebil" to become familiar with all topics you seek for.
The Biostar Handbook can give you a very good introduction to the terminologies, file formats, Linux command line , NGS data analysis and more. It also comes with updates for two years.